The biology of fracture healing is a complex biological process that follows specific regenerative patterns and involves changes in the expression of several thousand genes. Although there is still much to be learned to fully comprehend the pathways of bone regeneration, the over-all pathways of both the anatomical and biochemical events have been thoroughly investigated. These efforts have provided a general understanding of how fracture healing occurs. Following the initial trauma, bone heals by either direct intramembranous or indirect fracture healing, which consists of both intramembranous and endochondral bone formation. The most common pathway is indirect healing, since direct bone healing requires an anatomical reduction and rigidly stable conditions, commonly only obtained by open reduction and internal fixation. However, when such conditions are achieved, the direct healing cascade allows the bone structure to immediately regenerate anatomical lamellar bone and the Haversian systems without any remodelling steps necessary. In all other non-stable conditions, bone healing follows a specific biological pathway. It involves an acute inflammatory response including the production and release of several important molecules, and the recruitment of mesenchymal stem cells in order to generate a primary cartilaginous callus. This primary callus later undergoes revascularisation and calcification, and is finally remodelled to fully restore a normal bone structure. In this article we summarise the basic biology of fracture healing.

The biology of fracture healing

Carpal tunnel syndrome is one of the most common peripheral neuropathies. It affects mainly middle aged women. In the majority of patients the exact cause and pathogenesis of CTS is unclear. Although several occupations have been linked to increased incidence and prevalence of CTS the evidence is not clear. Occupational CTS is uncommon and it is essential to exclude all other causes particularly the intrinsic factors such as obesity before attributing it to occupation. The risk of CTS is high in occupations involving exposure to high pressure, high force, repetitive work, and vibrating tools. The classic symptoms of CTS include nocturnal pain associated with tingling and numbness in the distribution of median nerve in the hand. There are several physical examination tests that will help in the diagnosis of CTS but none of these tests are diagnostic on their own. The gold standard test is nerve conduction studies. However, they are also associated with false positive and false negative results. The diagnosis of CTS should be based on history, physical examination and results of electrophysiological studies. The patient with mild symptoms of CTS can be managed with conservative treatment, particularly local injection of steroids. However, in moderate to severe cases, surgery is the only treatment that provides cure. The basic principle of surgery is to increase the volume of the carpal tunnel by dividing transverse carpal ligament to release the pressure on the median nerve. Apart from early recovery and return to work there is no significant difference in terms of early and late complications and long-term pain relief between endoscopic and open carpal tunnel surgery.

Carpal tunnel syndrome

Bone replacement might have been practiced for centuries with various materials of natural origin, but had rarely met success until the late 19th century. Nowadays, many different bone substitutes can be used. They can be either derived from biological products such as demineralized bone matrix, platelet-rich plasma, hydroxyapatite, adjunction of growth factors (like bone morphogenetic protein) or synthetic such as calcium sulfate, tri-calcium phosphate ceramics, bioactive glasses, or polymer-based substitutes. All these substitutes are not suitable for every clinical use, and they have to be chosen selectively depending on their purpose. Thus, this review aims to highlight the principal characteristics of the most commonly used bone substitutes and to give some directions concerning their clinical use, as spine fusion, open-wedge tibial osteotomy, long bone fracture, oral and maxillofacial surgery, or periodontal treatments. However, the main limitations to bone substitutes use remain the management of large defects and the lack of vascularization in their central part, which is likely to appear following their utilization. In the field of bone tissue engineering, developing porous synthetic substitutes able to support a faster and a wider vascularization within their structure seems to be a promising way of research.

https://journals.sagepub.com/doi/pdf/10.1177/2041731418776819

Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Obesity is not protective against fracture in postmenopausal women: GLOW.

Risk factors for lymphoproliferative disorders after allogeneic hematopoietic cell transplantation

Background: Few data are available regarding the results of nonoperative treatment of distal biceps ruptures. The present study was designed to assess the outcomes associated with unrepaired distal biceps tendon ruptures.

Methods: Eighteen patients with twenty unrepaired distal biceps tendon ruptures were assessed retrospectively. The median duration of follow-up was thirty-eight months. Sixteen of the eighteen patients were male, and the median age at the time of the injury was fifty years (range, thirty-five to seventy-four years). Supination strength and elbow flexion strength were measured bilaterally, and patient outcomes were assessed with use of the Broberg and Morrey Functional Rating Index, the Mayo Elbow Performance Index, and the Disabilities of the Arm, Shoulder and Hand questionnaire. Data were compared with historical controls compiled from six published series of operatively treated patients.

Results: The median supination and elbow flexion strengths for the injured arm were 63% (mean, 74%; range, 33% to 162%) and 93% (mean, 88%; range, 58% to 110%) of those for the contralateral arm, compared with values of 92% (mean, 101%; range, 42% to 297%) and 95% (mean, 97%; range, 53% to 191%) for the historical controls that had been treated surgically. The difference between the mean values was significant for supination strength (p = 0.002) but not for flexion strength (p = 0.164). Patients had satisfactory outcomes overall, with median scores on the Broberg and Morrey Functional Rating Index, the Mayo Elbow Performance Index, and the Disabilities of the Arm, Shoulder and Hand questionnaire of 85, 95, and 9, respectively.

Conclusions: Nonoperative treatment of distal biceps tendon ruptures can yield acceptable outcomes with modestly reduced strength, especially supination.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Nonoperative treatment of distal biceps tendon ruptures compared with a historical control group.

The AAOS Evidence-Based Guideline on Management of Carpal Tunnel Syndrome (CTS) includes both diagnosis and treatment. This clinical practice guideline has been endorsed by the American Society for Surgery of the Hand (ASSH), the American College of Radiology (ACR), the American College of Surgeons (ACS), and the American Society of Plastic Surgeons (ASPS). This brief summary of the AAOS Clinical Practice Guideline contains a list of the recommendations and the rating of strength based on the quality of the supporting evidence. Discussion of how each recommendation was developed and the complete evidence report are contained in the full guideline at www.aaos.org/guidelines.

### OBSERVATION

Strong evidence supports that thenar atrophy is strongly associated with ruling in CTS but poorly associated with ruling out CTS.

Strength of Recommendation: Strong ★★★★ 

### PHYSICAL SIGNS

Strong evidence supports not using the Phalen test, Tinel sign, or upper limb neurodynamic/nerve test (ULNT) criterion A/B as independent physical examination maneuvers to diagnose CTS, because alone, each has a poor or weak association with ruling in or ruling out CTS.

Strength of Recommendation: Strong ★★★★ 

### MANEUVERS

Moderate evidence supports not using the following as independent physical examination maneuvers to diagnose CTS, because alone, each has a poor or weak association with ruling in or ruling out CTS:

The American Academy of Orthopaedic Surgeons Evidence-Based Clinical Practice Guideline on: Management of Carpal Tunnel Syndrome.

Understanding the anatomical relationships in the region of the supinator muscle is crucial in limiting surgical morbidity. The course, length, and muscular innervations of the posterior interosseous nerve, as well as a detailed dissection of the supinator muscle, were described and recorded in 31 specimens from 16 adult cadavers. In our study, the radial nerve bifurcated into the posterior interosseous nerve and superficial radial nerve 8.0±1.9 cm distal to the lateral intermuscular septum. The bifurcation of the radial nerve occurred 3.6±0.7 cm proximal to the leading edge of the supinator, with the posterior interosseous nerve exiting the supinator muscle 3.8±0.9 cm distal to the proximal margin. The arcade of Frohse was membranous in 68% of our specimens and tendinous in 32%. The supinator had one semicircular head or layer in 71% of specimens and 2 distinct heads or layers, as defined by diverging muscle fibers, in 29%. With 2 heads, or layers, the superficial layer extended to the lateral epicondyle while the deep layer extended to the ulna, below the radial notch.

The anatomical relationship between the posterior interosseous nerve and the supinator muscle.

Purpose Open release of A1 pulleys for trigger finger has been thought of as a relatively benign procedure with a low complication rate. Few studies have examined the rate of complications in trigger finger release. The objective of this study was to retrospectively review the complications documented for a cohort of patients who received open trigger finger releases. Methods We conducted a retrospective chart review of 43 patients who had had 78 open trigger finger releases by a single surgeon. Any postoperative complications that were documented were recorded. Complications were then divided into major and minor. Major complications required further surgery or resulted in significant limitations of activities of daily living; minor complications hindered recovery, responded to treatment (if applicable), and either resolved or had little impact on function. Results Two major complications were noted: a synovial fistula that required excision, and proximal interphalangeal joint arthrofibrosis that required cast application for pain relief. The major complication rate was 3% per trigger release (2/78). Twenty-seven minor complications in 22 digits were documented for these cases, including decreased range of motion, scar tenderness, pain, and wound erythema. The minor complication rate was 28% (22/78). The overall, combined complication rate for these primary interventions was 31% (24/78). Conclusions Open trigger finger release is thought to be a low-risk procedure by most practitioners. In this study, we found that major complications do occur infrequently; however, the rate of minor complications was surprisingly high and related mostly to wound complications or loss of finger range of motion. The surgeon performing open trigger finger releases should inform the patient of the likelihood of having these minor complications. Type of study/level of evidence Therapeutic IV.

Complications of open trigger finger release.

Charts of 28 patients with a diagnosis of delayed union or nonunion were reviewed. There were four delayed unions and 25 nonunions. Comorbidities, risk factors, treatments, and outcomes were evaluated. Comorbidities were common and included cardiovascular, pulmonary, and renal compromise, as well as endocrinopathies and rheumatologic disease. Consensus risk factors included: unstable fractures (comminuted or short oblique, 83% (24/29); advanced age, 57% (16/28); obesity, 35% (9/28); daily tobacco use, 38% (10/28); and multiple long bone fractures, 21% (6/29). Sixty-nine percent (20/29) of the fractures united; 21% (6/29) failed to heal. Healing outcome for 11% (3/29) could not be determined because of death or loss to follow-up. Patients presenting for primary treatment with any of the aforementioned risk factors should be cautioned regarding possible nonunion.

John D. Lubahn

Papers

Nonoperative treatment of distal biceps tendon ruptures compared with a historical control group.

The American Academy of Orthopaedic Surgeons Evidence-Based Clinical Practice Guideline on: Management of Carpal Tunnel Syndrome.

The anatomical relationship between the posterior interosseous nerve and the supinator muscle.

Complications of open trigger finger release.

Risk factors, treatment, and outcomes associated with nonunion of the midshaft humerus fracture.