Showing papers in "Clinical Orthopaedics and Related Research in 1994"

Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan

Abstract: A preoperative computed tomography (CT) scan grading muscular fatty degeneration in five stages was done in 63 patients scheduled for repair of a torn rotator cuff. The results were compared with postoperative evaluation done after a mean of 17.7 months in 57 patients. Postoperative arthrographies were also performed in 56 patients. Preoperative CT scans demonstrated that infraspinatus fatty degeneration can occur in the presence of large anterosuperior tears even when the infraspinatus tendon is not torn; it worsens with time. The subscapularis rarely degenerates, and when it does it degenerates moderately, even when its tendon is not torn. After an effective surgical repair, moderate supraspinatus degeneration regressed in six of 14 patients; that of the infraspinatus never regressed but rather, increased, in three patients. One of these deteriorations, involving both supra- and infraspinatus, could probably be attributed to a partial subscapular nerve injury. Infraspinatus degeneration was correlated with functional pre- and postoperative impairment of active external rotation. Recurrence of infraspinatus tear was never observed, but recurrence occurred in 25% of supraspinatus repairs. Infraspinatus degeneration had a highly negative influence on the outcome of supraspinatus repairs. It seems preferable to operate on wide tears before irreversible muscular damage takes place.

Postoperative alignment of total knee replacement. Its effect on survival.

Abstract: Four hundred twenty-one posterior cruciate condylar total knee arthroplasties were performed between 1975 and 1983. Anatomic alignment of the knee was recorded on follow-up evaluations from two months to 13 years postoperatively. Patients were stratified into a normal group that was 5 degrees to 8 degrees anatomic valgus, a varus group that was from 4 degrees anatomic valgus to any degree of varus, and a valgus group that was more than 9 degrees anatomic valgus. There were eight failures, five in the varus group and three in the normal group. There were no failures in the valgus group. Kaplan-Meier survival curves showed no significant difference between normal and valgus groups; however, there was a statistical difference between the valgus and varus and the normal and varus groups. A surgeon should align a total knee prosthesis in neutral or a slight amount of anatomic valgus to give the patient the best chance for long-term survival.

The incidence of fractures of the clavicle.

Abstract: The age- and gender-specific incidences were calculated in 2035 cases of fracture of the clavicle. The fractures were classified in three groups according to the Allman system. Each group was further divided into undisplaced and displaced fracture subgroups, with an extra subgroup of comminuted midclavicular fractures in Group I. Seventy-six percent of the fractures were classified as Allman Group I. The median age in this group was 13 years. There were significant differences in age- and gender-specific incidence between the undisplaced, displaced, and comminuted fracture subgroups. Twenty-one percent were classified as Allman Group II. The median age of the patients was 47 years, and there was no difference in age between the undisplaced and displaced fracture subgroups. Three percent were classified as Allman Group III, and the median age of the patients in this group was 59 years. All three groups were characterized by a significant preponderance of men, and there was a significant increase in the incidence of clavicular fracture, both overall and sports-related, between 1952 and 1987.

Wear patterns on retrieved polyethylene tibial inserts and their relationship to technical considerations during total knee arthroplasty.

Abstract: Fifty-five unconstrained polyethylene tibial inserts were retrieved at revision total knee arthroplasty and examined for evidence of wear after a mean implantation time of 34.2 months (2.5-80 months). Twenty inserts were ultra-high molecular weight polyethylene (UHMWPE) and 35 were carbon-reinforced polyethylene. Topographic maps of the articular and metal-backed surfaces of each component were constructed to characterize the extent and location of polyethylene degradation, identified visually by mode. In 32 of the retrieved inserts, pre- and postarthroplasty or prerevision radiographs were analyzed for component positioning, sizing, and extremity alignment. These factors then were compared with the patterns and severity of polyethylene wear on the inserts to establish correlations. Severe generalized articular wear was seen in inserts with third body wear from patellar metal-backed failure and cement debris. Severe localized delamination wear was seen in inserts with rotational-subluxation patterns of wear (p = 0.05). The external rotation subluxation wear pattern was strongly associated with knees that had lateral subluxation of the patella (p = 0.0002). Articular wear and cold flow into screw holes tended to be greater in the tightest prearthroplasty compartment (medial in the varus knee [p = 0.0157]; lateral in the valgus knees [p = 0.0226]). Fourteen of 16 knees with a preoperative varus deformities--even when corrected to a normal postarthroplasty anatomic axis--still had greater medial compartment articular wear (p = 0.001). Twelve of these knees did not have a medial release at the time of initial arthroplasty. Preoperative varus also was found to be related to the occurrence of posteromedial cold flow of polyethylene into tibial tray screw holes (p = 0.007). Increasing tibial insert posterior slope was associated with increasingly posterior articular wear track location (p = 0.03). This study indicates that unconstrained tibial component wear patterns and severity may be associated with clinical and mechanical factors under the surgeon's control, including component size and position, and knee alignment and ligament balance.

Functional and anatomical results after rotator cuff repair.

Abstract: The anatomic condition of the rotator cuff and the functional results obtained were studied in a homogeneous series of 100 full thickness cuff tears in 98 patients with an average followup of 4 years. Constant's functional score, used by the European Society for Shoulder and Elbow Surgery, was done preoperatively and postoperatively in each patient, in addition to ultrasonography at followup. There was a close correlation between the anatomic condition of the cuff and Constant's functional score before surgery (p = 0.0063) and after repair, irrespective of the type of tear repaired (p = 0.0012) or the sonographic appearance of the cuff at followup (p = 0.0001). Ultrasonography showed 65% intact cuffs, 11% intact but thinned cuffs, and 24% recurrent defects. Three predisposing factors for recurrence were noted: size of tear to be repaired (p = 0.0001) accounted for 57%, age (p = 0.063) for 25%, and degree of occupational use for 18%. The functional results obtained were more related to the anatomic condition of the repaired cuff at followup than to the tear size at surgery. Predictive clinical factors for recurrence included overall Constant's functional score, reduced ability to perform daily activities, reduced active flexion, abduction and external rotation, and loss of muscular strength. Constant's functional score reflected the functional results with accuracy, reliability, and reproducibility. Additional ultrasonography appears necessary to specify the exact size of the recurrent defect and to distinguish between certain anatomic types, such as thinned cuffs, which can give rise to difficult problems in manual workers after defect repair.

Complications of shoulder arthroplasty

Abstract: Early and mid-range followup studies of shoulder arthroplasty have been encouraging, showing good and excellent results in > 90% of shoulders. Despite this success, complications in shoulder replacement surgery are inevitable, with an incidence of approximately 14%. Numerous complications have been identified and include the following factors in order of decreasing frequency: instability, rotator cuff tear, ectopic ossification, glenoid component loosening, intraoperative fracture, nerve injury, infection, and humeral component loosening. Successful treatment of these difficulties requires careful identification and subsequent analysis of all factors contributing to the complication, knowing that the etiology is often multifactorial. Failed shoulder arthroplasty can be successfully managed with revision surgery, but the technically challenging surgery and the overall results are inferior compared with other diagnostic categories.

Recombinant Human Bone Morphogenetic Protein-7 Induces Healing in a Canine Long-Bone Segmental Defect Model

Abstract: An ulnar segmental defect model was used in adult male dogs to examine the effect of recombinant human bone morphogenetic protein-7 (recombinant human Osteogenic Protein-1 [rhOP-11; Creative Biomolecules, Hopkinton, Massachusetts) on new bone induction and healing, and to test the mechanical strengt

Acetabular fracture fixation via a modified Stoppa limited intrapelvic approach. Description of operative technique and preliminary treatment results

Abstract: Between March 1991 and December 1992 the authors surgically treated 55 acetabular fractures using a modified Stoppa anterior intrapelvic extensile approach. Indications for utilization of this approach included displaced anterior column or wall fractures, transverse fractures, T shaped fractures, both column fractures and anterior column or wall fractures associated with a posterior hemitransverse component. The approach involves a transverse skin incision 2 cm above the pubic symphysis followed by a midline split of the rectus abdominis. Access to the intrapelvic aspect of the pelvis and acetabulum is gained by retraction of the muscular, neurovascular and urological structures. This modified Stoppa approach affords excellent visualization of the pelvic ring, facilitating the development and utilization of improved reduction and plating options. Patients were followed for an average of 17.7 months. All fractures united 6-12 weeks postoperatively. Radiographic grades were excellent (64%), good (25%), fair (7%) and poor (4%). Fixation and subsequent reduction were lost in 1 patient. Two transient obturator nerve palsies were diagnosed. There was 1 infection and 1 inguinal hernia. Posttraumatic arthritic changes were noted in 6 patients within the first postoperative year. There was no significant heterotopic ossification, major vascular injury iatrogenic palsy or intraarticular hardware placement. Clinical results were excellent (47%), good (42%), fair (9%) and poor (2%). The modified Stoppa incision offers the experienced trauma surgeon a new approach for fixation of displaced acetabular fractures. The approach offers improved reduction and fixation possibilities and may decrease the rate of complications associated with extrapelvic or extensile approaches.

Complications of limb lengthening. A learning curve.

Abstract: Major complication rates during limb lengthening were plotted in a consecutive series to produce a learning curve. All unwanted events during and after treatment were considered complications, and graded as minor, serious, and severe. All serious and severe complications were considered major. A novel system was used to classify the preoperative severity of each deformity. One-hundred ten patients had 140 bone segments lengthened between 2.2 cm and 10.5 cm, with a mean of 4.4 cm. Three methods were used in lengthening: the Wagner method in 22 patients, the DeBastiani method in 34 patients, and the Ilizarov method in 84 patients. Ninety-eight complications categorized as serious or severe occurred, for a total major complication rate of 72%. The percentage of major complications began to drop after 30 lengthenings to a current rate of 25%. Major complications were frequent in patients with more severe deformities, particularly in those whose cases occurred early in the series. Bone healing complications were high (72%) in the Wagner segments but were also high (80%) in the first ten patients treated with the DeBastiani technique. The first ten Ilizarov patients, who were treated later in the series, had a 40% rate of bone-healing complications. The current rate of major complications is 13% for those patients treated with DeBastiani's method and 33% for those patients treated with Ilizarov's method. This difference in complication rates appears to relate to the severity of the deformity, rather than the device used. There was a significant decrease in complications as experience was gained. Directed formal study and surgical instruction should help diminish these complications.

Innervation of the human knee joint and implications for surgery.

Abstract: The anatomy of the articular and cutaneous nerves about the knee was investigated through 45 dissections of human anatomic specimens. The variability and location of these nerves are described and related to soft tissue and bony landmarks. Three constant nerves exist at the medial aspect of the knee, two of which have cutaneous territories that extend across the midline. The third nerve is articular. Two lateral articular nerves were found consistently in relation to reliable landmarks. The innervation to the lateral knee skin is variable from either the lateral femoral cutaneous nerve or branches of the femoral nerve. This anatomy provides a basis for nerve blocks and selective denervation in the treatment of knee pain.

The Hannover experience in management of pelvic fractures

Abstract: Between 1972 and 1993, 1899 patients with fractures of the pelvis were treated at the authors institution. The pelvic ring was fractured in 1479 patients, and 1029 sustained polytrauma. A retrospective study included four parts: (1) Demographic analysis of 1409 patients showed an increase in the severity of pelvic and general trauma during this period. The 17.7% mortality rate was predicted by the Hannover Polytrauma Score and associated extrapelvic blunt trauma. (2) Residual displacement after operative treatment of the pelvis was analyzed in 221 patients. In C type (Tile) fractures residual displacement correlated with external fixation and solely anterior stabilization. (3) Outcome after operative treatment was analyzed in a consecutive series of 58 patients an average of 2.2 years after trauma. Pelvic pain was frequent (Type B 11%, Type C 66%) and correlated with posterior displacement over 5 mm and primary neurological injuries. (4) Mortality after complex pelvic trauma (pelvic fracture with soft tissue injury) decreased from 48.1% to 29.6% during these years. Standardized protocols for primary care and operative procedures of pelvic injuries optimize therapy. Complex pelvic trauma requires early, aggressive surgical management with surgical hemostasis. Further developments in open reduction and internal fixation of the pelvis focus on minimizing additional soft tissue trauma and implants.

Determinants of outcome in the treatment of rotator cuff disease.

Abstract: One hundred thirty-six patients with impingement syndrome and rotator cuff disease who were treated nonoperatively from 1987 to 1991 were reviewed to identify findings at initial presentation that correlated with final outcome. Mean followup was 20 months (range, 6-41 months). All patients received initial conservative treatment. The results were analyzed in 2 groups. Group I consisted of the entire 136 patients with a minimum 6-month followup. Group II consisted of a subgroup of 68 patients with at least an 18-month followup. The overall results in Group I were 66% excellent and good and 34% fair and poor. For Group II, the overall results were 76% excellent and good and 24% fair and poor. For the Group II patients, a distribution of clinical findings at the 6-month followup demonstrated only 46% excellent and good results, indicating that the clinical result improves significantly as followup duration increased. Patient characteristics and prognostic factors that were associated with an unfavorable clinical outcome included a rotator cuff tear > 1 cm2, a history of pretreatment clinical symptoms for > 1-year duration, and significant functional impairment at initial presentation. Factors not associated with clinical outcome included patient age, occupation, gender, associated instability, dominance, chronicity of onset, active range of motion, or specific treatment modalities. Early operative intervention is recommended for patients with poor prognostic factors to avoid a protracted clinical course.

Variables affecting time to bone healing during limb lengthening.

Abstract: Radiographs and charts of 114 consecutive patients who underwent 140 lower-extremity bone-segment lengthening procedures using the Ilizarov external fixator were reviewed. Patient age, bone segment (femur, tibia), corticotomy level (metaphyseal, diaphyseal, double level), and distraction gap (DG) were recorded. Distraction-consolidation time (DCT) was defined as the interval in months from the date of the corticotomy until the DG was healed according to radiographic and manual testing criteria. Distraction-consolidation time had a direct linear relationship with the magnitude of the DG. Distraction--consolidation time versus DG was significantly less for femoral than tibial lengthening. Patients 20 years and older healed slower than patients younger than the age of 20 years. Patients 20 to 29 years old healed faster than patients older than 30 years and slower than patients younger than 20 years. Diaphyseal lengthening healed more slowly than metaphyseal lengthening. Double-level lengthening reduced the DCT when the DG was greater than 4 cm. Distraction--consolidation index--DCT divided by DG--was not a constant. Distraction--consolidation index decreased with increasing DG. To facilitate prediction of bone-healing time, graphs were developed demonstrating the average treatment time +/- 2 SD expected for a specific amount of lengthening, considering the bone segment, the level of osteotomy, and the age of the patient.

Open reduction and internal fixation of fractures of the acetabulum. Results in 163 fractures

Abstract: Management of displaced fractures of the acetabulum represents one of the greatest challenges in fracture surgery. This study reports intermediate term results for a single surgeon of 163 fractures in 161 patients treated by open reduction and internal fixation. The mean length of followup was 3.7 years. The most common fracture patterns treated were both column (67), transverse/posterior wall (32), posterior wall (14), and T shaped (12). The surgical approaches chosen were ilioinguinal (86), Kocher-Langenbeck (58), and extended iliofemoral (26) with 7 patients having sequential or simultaneous dual approaches. Reductions were rated by plain radiography and considered anatomic in 93 (56%) and near anatomic (< 2 mm displacement) in 40 (25%). There were 7 (4%) infections, 2 (1%) vascular injuries, 3 (2%) sciatic injuries, and 1 (1%) obturator nerve injury. Overall outcome was rated as excellent in 23 (14%), good in 101 (61%), fair in 25 (16%), and poor in 14 (9%). Nine patients have undergone hip salvage procedures. These results add to the growing body of clinical data which validates open reduction as the treatment of choice in most displaced fractures of the acetabulum.

Indications for surgical treatment of tibial condyle fractures.

Abstract: The residual radioanatomic changes influencing the functional, subjective, and clinical outcome of 131 tibial condyle fractures were studied. Clinical function was found to deteriorate rapidly with increasing values of residual medial tilt of the tibial plateau, whereas lateral tilt of the plateau w

The Classic: On the Means of Lengthening, in the Lower Limbs, the Muscles and Tissues Which are Shortened Through Deformity

Abstract: The difficulties to be encountered in lengthening a shortened limb, are found, in operation, to be greater as regards the fleshy parts, than as regards the bones. It is comparatively easy to remove the splinters of a fractured bone which is wrongly consolidated; to separate a curved bone; or to perform an oblique osteotomy, but a decided limit is arrived at in the correction of a displacement, or in the lengthening of the bones, by reason of the contraction, or resistance, of the muscles. Our supreme consideration must therefore be given in striving to overcome this resistance on the part of the muscles, without however damaging in any way the action of the tissues. This is the special subject on which I desire to enlarge, as it appears to me that this important part in the cure of deformity of the limbs, has never been sufficiently taken into consideration.

Promotion of bony ingrowth by frequency-specific, low-amplitude mechanical strain.

Abstract: The ability of extremely low-amplitude mechanical strains to promote bony ingrowth was evaluated in an in vivo animal model, the functionally isolated turkey ulna. A cylindrical, porous-coated titanium implant was placed across the dorsal and ventral cortices of the left ulna diaphysis of 12 animals

Temporal and spatial increases in blood flow during distraction osteogenesis.

Abstract: Ten adult mongrel dogs underwent left tibial lengthening at the proximal metaphysis. They were divided into three groups on the basis of distraction period: 14, 28, and 56 days. Quantitative technetium scintigraphy was used to measure regional blood flow within the tibiae during distraction, and periodically during consolidation, up to 17 weeks after operation. Blood flow was measured from regions of interest during the flow phase of the scan and expressed as a ratio of lengthened side to control side. At the distraction site, the flow increased to nearly ten times control, peaked at two weeks postoperatively, then decreased to four to five times the control for the remainder of the distraction period. During the consolidation period, significantly increased flow persisted at levels of two to three times control. The distal tibiae, away from the distraction gap, showed similar amplitude and temporal patterns of increased flow. No significant differences were found between the groups tested or when compared with similar fracture models. These findings lend credence to Ilizarov's hypothesis that distraction osteogenesis may contribute to healing of chronic osteomyelitis or hypovascular nonunions at distant sites by inducing a prolonged hypervascular state. Whether distraction osteogenesis transforms the normal reparative response of bone injury to a regenerative response remains conjectural.

Fresh osteochondral allografts for treatment of articular defects in osteochondritis dissecans of the lateral femoral condyle in adults.

Abstract: Fresh osteochondral allografts were used to patch defects in the lateral femoral condyle in 17 patients with osteochondritis dissecans. The patients included 12 males and five females, ages 16 to 46 years. All had previously undergone other procedures including pinning (4), primary removal of osteochondral fragments (16), and abrasion arthroplasty (14). Defects up to 3 cm in diameter were treated with isotopic grafts and fixed with Herbert screws. Larger defects were treated with crescent-shaped grafts fixed with multiple Herbert screws. Follow-up time ranged from two to nine years. Pain, stiffness, swelling, buckling, and locking were ablated in 16 of the 17 patients. No graft collapse has been noted in these individuals. Verification of graft viability was achieved at periods from six weeks to six years, typically at the time of hardware removal. The only failure occurred in an individual with a 3- x 4.5-cm defect who suffered gross fragmentation which left a large crater. Osteochondritis dissecans of the lateral femoral condyle provides an ideal opportunity for evaluating osteochondral grafts. Sixteen of 17 grafts were a success at two to nine years after surgery.

The joint side tear of the rotator cuff. A followup study by arthrography.

Abstract: A clinical followup study was performed of joint side tears of the rotator cuff to define the pathogenic mechanisms and factors that affect their evolution. From 1982 to 1992, the authors treated 61 joint side tears, diagnosed by arthrography. Among them, 40 tears were followed-up during conservative treatment. Arthrographies were repeated at a mean of 412 days. There were 16 male and 20 female patients, with a mean age of 61 years. Two male and two female patients had bilateral tears. The average shoulder assessment score according to the Japanese Orthopaedic Association rating at the initial visit to the hospital was 68 points, and 80 points at followup time. Followup arthrographies revealed disappearance of the torn portion in four instances, reduction of the tear size in four, enlargement of the tear size in 21, and progress to full thickness cuff tear in 11 patients. Prognosis of the joint side tear appears to be worse with increasing age, larger tear size, and absence of history of trauma.

Segmental tibial defects. Comparing conventional and Ilizarov methodologies.

Abstract: Forty-four consecutive patients with segmental debridement defects of the tibia had limb-salvage surgery. Twenty-one patients (Group I) were managed using methods as described by Ilizarov. Twenty-three patients (Group II) underwent conventional treatment with massive cancellous grafts and tissue transfers. Total wound consolidation and infection arrest took place after the first treatment in 71% of the Ilizarov wounds and 74% of the conventionally treated wounds. The major complication rates were 33% and 60% for Groups I and II respectively. The patient population at highest risk for failure was the compromised host treated conventionally (44%). The cost for retreatment and overall success rate (95%) were the same for both groups. Ilizarov reconstructions averaged nine fewer hours in the operating theater, 23 fewer days in the hospital, five fewer months' disability (17 months versus 22 months), and a savings of nearly $30,000 per application.

The characterization of cytokines in the interface tissue obtained from failed cementless total hip arthroplasty with and without femoral osteolysis.

Abstract: The histologic, biochemical, and immunohistologic characteristics of the interface membranes surrounding the femoral component of failed cementless total hip arthroplasty (THA) in patients with (Group I) and without (Group II) radiographic evidence of focal endosteal erosion (osteolysis) were studied. Group I membranes had more macrophages and small particles of polyethylene debris in the membrane, but both groups had similar amounts of metal particles. A greater activity level of interleukin-1 (IL-1), tumor necrosis factor (TNF), and interleukin-6 (IL-6) was seen in the culture supernatant of the membranes from Group I than in that of Group II. Group I membranes also had more cells (macrophages, fibroblasts, and endothelial cells) that stained positively with anti-IL-6 antibody. These results suggest that IL-6, IL-1, and TNF play a role in the focal femoral osteolysis observed in patients with failed cementless hip prostheses.

Complications with hydroxyapatite particulate separation in total hip arthroplasty.

Abstract: This study reports on the results of the implant and tissue analysis of clinically retrieved hydroxyapatite (HA)-coated implants. Five of the patients with fixed HA-coated stems had been clinically diagnosed with osteolysis. The semiquantitative histologic grading in these patients showed HA, polyethylene, and metal particles were all present (Grade 3+) in the osteolytic regions of the periprosthetic tissue. Additionally, inflammatory cells (Grade 3+) were present in these regions. Back-scattered electron (BSE) and correlated elemental analysis showed HA particulate was present in the polyethylene inserts. The HA could be distinguished from bone chips in the polyethylene based on morphology and anatomic number gray level differences. This study was limited in that no clinical results of particular HA-coated implant series were reported. Careful follow-up care in patients with coated devices is recommended.

Skeletal defects. A comparison of bone grafting and bone transport for segmental skeletal defects.

Abstract: To evaluate two different methods of managing segmental skeletal defects, 15 patients treated with the open bone graft (Papineau) technique were compared with 17 patients who had intercalary bone transport (Ilizarov) management. The treatment time was identical for both groups: 1.9 months in fixation for each centimeter of defect reconstructed. Both techniques shared several fixator-associated problems such as implant site sepsis and patient discomfort. Each method of treatment, however, had its own unique problems. For the bone grafted group, limited graft availability, donor site morbidity (three patients), and graft fractures (two patients) occurred. For the bone transport group, the main problems were failure of the docking site to unite without a supplementary graft (seven patients) and joint contractures (seven patients). A new synthesis of both techniques is described.

Concerns With Modularity in Total Hip Arthroplasty

Abstract: Modularity is being diversified in total hip prostheses to increase surgical latitude in optimizing implant fixation and adjusting hip biomechanics. However, several problems have been clearly identified with implant modularity. First generation metal-backed acetabular components have shown deficien

Operative treatment of acetabular fractures through the ilioinguinal approach. A 10-year perspective.

Abstract: The ilioinguinal surgical approach was found to be effective for treatment of 119 (about 33%) of the 373 acetabular fractures treated operatively by the author over a 10-year period. It is indicated for anterior wall, anterior column, associated anterior and posterior hemitransverse fractures, as well as certain both column and transverse fractures. The approach offers the advantages of a cosmetic incision, rapid recovery of muscle function, and minimal ectopic bone formation. Complications included 3% surgical wound infection, 2% iatrogenic nerve palsy, 1% significant ectopic bone, and 1% death from pulmonary embolus. Clinical results at a minimum of 1-year, and an average of 3-years' followup, were, excellent in 37%, good in 47%, fair in 14%, and poor in 2%. Two patients later required total hip arthroplasty for posttraumatic arthritis.

The influence of fixed rotational deformities of the femur on the patellofemoral contact pressures in human cadaver knees.

Abstract: Patellofemoral contact pressures resulting from fixed rotational deformities of the femur were studied in human cadaver knees. The increase in the degree of fixed rotational deformities of the femur results in a nonlinear increase in patellofemoral contact pressures on the contralateral facets of the patella (i.e., external rotational deformity resulted in a contact pressure increase on the medial facet, and internal rotational deformity resulted in a contact pressure increase on the lateral facet of the patella). With the initial isometric tension of 200 N in the quadriceps tendon for 30 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion, the peak contact pressure showed no significant differences between the medial and lateral facets of the patella in its anatomic position. At 20 degrees of rotational deformity of the femur, only a slight increase was noted for the tension in the quadriceps tendon and the patellofemoral contact pressures on the contralateral facets of the patella. However, at 30 degrees rotational deformity of the femur, both the external and internal rotational deformity of the femur showed a significant increase in the tension of the quadriceps tendon and the patellofemoral contact pressures on contralateral facets of the patella. The greatest increase in patellofemoral contact pressures was observed at 30 degrees and 60 degrees knee flexion for both the external and internal rotational deformity of the femur. The external rotational deformity of the femur for all knee flexion angles showed significantly higher peak patellofemoral contact pressure increases on the medial facet of the patella as compared with the lateral patellofemoral contact pressure increase resulting from internal rotational deformity of the femur.

Implant failure and the immuno-incompetent fibro-inflammatory zone.

Abstract: Biomaterial implants are surrounded by an immuno-incompetent, fibro-inflammatory, integration-deficient zone within which stimulation of cellular immune responses results in superoxide radical and cytokine-mediated tissue damage with increased susceptibility to infection or aseptic loosening. Three important questions that pertain to surgical implants are (1) What are the mechanisms that cause abnormal inflammatory responses in the absence of infection and result in interface cellular disorganization and device failure? (2) What causes host defenses to be compromised to the extent that normal flora organisms like Staphylococcus epidermidis, with little or no virulence potential, can cause life-threatening infections at the implant-host interface? (3) What is the nature of surface regions of biomaterials that facilitate bacterial adherence? Pathogenic strains of S. epidermidis and Staphylococcus aureus have an affinity for biomaterial surfaces and are capable of initiating infection. Binding may be nonspecific and glue-like rather than a receptor-ligand event as for S. aureus and matrix proteins. This study indicates bacterial binding to sites of higher vanadium concentration at grain boundaries and mixed phases in titanium alloys. Repeated macrophage priming by biomaterial particulates results in the production of reactive oxygen intermediates, macrophage exhaustion, and adjacent tissue damage. A cytokine cascade is also initiated. A self-perpetuating enlarging immuno-incompetent fibro-inflammatory zone develops about implants, which features tissue cell damage, increased susceptibility to infection, and results in septic or aseptic failure of the implant. These effects are clearly exemplified by fibrosis about breast implants and osteolysis at the interface of total joint replacements.

Treatment of the infected total hip arthroplasty with a two-stage reimplantation protocol.

Abstract: Forty-four patients (46 hips) with infected total hip arthroplasties were evaluated. They were entered into a protocol that included resection arthroplasty, six weeks of intravenous antibiotics which obtained a minimum postpeak serum bactericidal titer of 1:8, and possible reimplantation. Thirty-two of 46 hips (70%) were reimplanted. At an average of 40 months (range, 24-74 months) after reimplantation, infection recurred in three hips (9%). In two of the three recurrent infections, 1:8 bactericidal titers were not attained. Both of these hips were infected with gram-negative organisms. Minimum postpeak serum bactericidal titers of 1:8 were attained in 28 of 32 hips that were reimplanted, and only one of these hips (4%) had a recurrent infection (p = 0.035). The presence of retained cement after resection arthroplasty (ten hips) was not associated with recurrent infection. Fourteen hips (12 patients were not reimplanted as a result of a combination of factors, including inadequate bone stock, poor soft-tissue quality, and antibiotic resistance of the infecting organism. The treatment of an infected total hip arthroplasty with resection arthroplasty, six weeks of intravenous antibiotics that attains a minimum postpeak serum bactericidal titer of 1:8, and reimplantation can be an effective and safe treatment.

Long-term survival analysis of a posterior cruciate-retaining total condylar total knee arthroplasty.

Abstract: From 1975 to 1983, 278 patients received 418 posterior cruciate ligament-retaining Total Condylar knee arthroplasties. Twenty-four patients were excluded, 15 for lack of followup data, 6 for infection during followup, and 3 for revision surgeries for previous infections. The 394 remaining knees were observed from 1 to 18 years (mean, 8.08 years). Kaplan-Meier and crude survival estimates at 12 years were 96.8% and 98.1%, respectively. Various survival analyses by other authors have yielded similar successful results