Broken MAN
Patients who undergo transtibial amputation must exert which percentage of increased energy for ambulation as compared to baseline?
40%
Patients who undergo transfemoral amputation exert 65% more energy for ambulation compared to baseline. Patients with transtibial amputations exert 25% more energy compared to baseline.
Metal allergy has been found to be associated with continued pain after knee arthroplasty. What metal most commonly provokes allergy after surgery?
Nickel
Metal allergy does not very commonly cause failure after total knee arthroplasty, but it does cause continued pain and symptoms for some patients. The most common metal allergy is to nickel, followed by cobalt and then chromium. Titanium, vanadium, tantalum, and alumina are materials that are relatively inert and commonly do not cause allergic reactions.
A 55-year-old man sustains a fall off of a two-step ladder and has pain and weakness in his right shoulder. His MRI scan shows medial subluxation of his biceps. What physical examination would confirm this finding?
Abdominal compression test
Medial subluxation of the biceps tendon is indicative of a tear of the upper border of the subscapularis tendon. On physical examination, this would be identified by a positive belly press test. A positive empty can test implies injury to the supraspinatus, the external rotation lag sign indicates injury to the external rotators, and the Hornblower test is indicative of injury to the teres minor.
A 34-year-old man has ulnar hand numbness and an inability to cross his index and middle fingers. The symptoms have been present since he completed a 2-day bicycle trip 5 weeks earlier. The initial diagnostic workup should include
The scenario described is most consistent with handlebar palsy, or ulnar tunnel syndrome, caused by prolonged compression of the ulnar nerve as it passes through the Guyon canal. A nerve study would demonstrate changes consistent with acute focal demyelination. MRI of the cervical spine would be appropriate in the setting of radiculopathy. An angiogram could be considered if a wrist ultrasound showed an ulnar artery pseudoaneurysm, but not as an initial study in this situation. CT of the wrist would be appropriate if a hook of the hamate fracture was suspected.
A 27-year-old woman with a known hemangioma in the medial gastrocnemius muscle has failed to control her symptoms with nonsurgical measures or sclerotherapy. What is the best next treatment option?
Marginal resection
This patient has a symptomatic benign vascular tumor that has failed sclerotherapy. In this case, surgical resection is an appropriate treatment option, particularly given that the expected morbidity is low. The lesion is benign; therefore, radiation and cytotoxic chemotherapy are generally inappropriate. Targeted agents may play a role in management, particularly for multifocal disease.
The radiographic view that best depicts the supra-acetabular corridor during placement of an anterior pelvic external fixator is the
Obturator outlet
In the management of pelvic fractures, external fixator placement is common. The placement of supra-acetabular Schanz pins and pedicle screws requires visualization of the supra-acetabular corridor, which is best seen on the combined obturator outlet oblique view of the pelvis. Other views are also important for the safe placement of pins and screws.
Tendons are primarily composed of
Type I collagen
Tendons belong to a family of dense connective tissues that are composed of mostly parallel collagen fiber bundles. They are primarily composed of type I collagen, with a smaller percentage of minor collagens, proteoglycans, elastin, and water.
A 77-year-old man has had 2 years of left shoulder pain and weakness that has worsened despite multiple corticosteroid injections and two trials of physical therapy. On examination, his left shoulder has decreased range of motion with pain. MRI shows cuff tear arthropathy with full-thickness tears of the supraspinatus, infraspinatus, and teres minor, with retraction to the glenoid and significant muscle atrophy. What is the most appropriate treatment?
Reverse shoulder arthroplasty with latissimus dorsi transfer
This patient has long-standing cuff tear arthropathy that has failed nonsurgical management. Given the chronicity of the tear, significant atrophy, and retraction, arthroscopic repair is not a preferred option. Reverse shoulder arthroplasty is the preferred treatment, but given the patient’s teres minor tear, this procedure should be performed with a concurrent latissimus dorsi transfer. Cuff tear hemiarthroplasty is not preferred, because the patient does not have retained forward flexion.
What is the most important factor leading to the redisplacement of an adequately reduced distal forearm fracture in the pediatric population?
The cast index is derived by dividing the sagittal width by the coronal width measured on radiographic images as the inner surface of the plaster cast in both views. Several studies have demonstrated that an index greater than 0.8 is associated with a higher postreduction loss of angular alignment. In simple terms, an adequate cast mold resulting in an oval cast provides substantially more stability than a circular cast. The remaining indices were not found to be independently predictive of redisplacement. The padding index is measured as the dorsal gap at the fracture site on the lateral view divided by the maximum interosseous space on the AP view. The second metacarpal-radius index is measured as the angle created by bisecting the long axis of the index metacarpal and the long axis of the radius on the AP view. The Canterbury index is calculated as the sum of the cast index and the padding index.
A 98-year-old man who is right-hand dominant is being evaluated for a dorsal left hand mass that was recently removed by another surgeon. Pathology results reveal findings consistent with a high-grade sarcoma. Information regarding margin status is unavailable. What is the best next step?
Wide re-excision
Unplanned excisions of soft-tissue sarcomas have a high risk of local recurrence. Tumor bed re-excision is recommended unless it will impart substantial morbidity. Adjuvant radiation therapy is often used to improve local control; however, instances occur in which its use is unnecessarily morbid. Cytotoxic chemotherapy is likely contraindicated in a nonagenarian.
The incidence of heterotopic ossification (HO) in the surgical management of acetabular fractures can be reduced by debridement of the
Gluteus minimus
HO is a common complication after the surgical management of acetabular fractures. It has an incidence ranging from 7% to 100%. Substantial discomfort, stiffness, and poor functional outcomes can be seen in patients with HO. The etiology is multifactorial, and the surgical approach to the acetabular fracture pattern is an important factor in successful management. Debridement of a contused gluteus minimus could prevent the formation of HO. Posterior wall fractures and transverse-posterior wall fractures treated through the Koch-Langenbeck approach have an intermediate risk of developing HO. Debriding the damaged gluteus minimus muscle and single-dose radiation have been shown to decrease the incidence of HO. A low incidence of HO has been seen with the ilioinguinal and the Stoppa approaches, an intermediate incidence with the Kocher-Langenbeck approach, and a high incidence with the extended-iliofemoral approach.
The most abundant type of collagen in articular cartilage is
Type II
Articular cartilage is made up of types II, VI, IX, X, and XI collagen. Of these, the most abundant collagen in cartilage is type II.
A 46-year-old woman reports having right shoulder pain for the last 6 months without any antecedent trauma. On physical examination of the right shoulder, her active forward elevation is 160°, abduction is 150°, and external rotation in adduction is 25°. This is the same as passively with pain at the end range of motion in all planes. The left shoulder has normal range of motion. She has negative results for the abdominal compression test, Hornblower test, and external rotation lag sign. MRI scan shows a partial articular side supraspinatus tear. She has had no previous treatment. What is the best next step?
Physical therapy with a focus on range of motion
This patient has a classic case of adhesive capsulitis, with an insidious onset of decreased range of motion in all planes, which is worse in external rotation in adduction. It is not unusual for MRI to demonstrate some mild rotator cuff pathology in these patients. The initial mainstay of treatment is physical therapy focusing on range of motion.
Posterolateral instability of the elbow typically occurs as a result of
Posterolateral rotatory instability typically occurs as a result of a fall on an outstretched arm, with the elbow initially in the extended position, and involves axial load, valgus force, and supination. As an axial load is applied to the arm, the elbow sustains a valgus moment, and the distal humerus internally rotates or supinates against the forearm that is fixed to the ground. The result is disruption of the lateral collateral ligament as the radial head and coronoid rotate posterolaterally off the distal humerus.
A 76-year-old diabetic man reports having a left distal thigh mass over the previous 6 months. A resection was performed. Pathology was consistent with a high-grade sarcoma involving the surgical margins. What is the best next step?
Wide resection and photon therapy
Unplanned excisions for large soft-tissue sarcomas generally are managed with re-resection and radiation therapy. Several ways to deliver ionizing radiation are available. Conventional radiation utilizes photons delivered through a number of technologies, including intensity-modulated radiotherapy. Proton beam radiotherapy offers the added value of avoiding the exit dose and therefore is often used in the context of spinal column tumors or tumors immediately adjacent to the spinal elements.
Even with a stable, anatomic reduction of the articular surface, the risk of posttraumatic arthritis after intra-articular ankle fracture is significant. In addition to direct injury to the cartilage, what factor most likely contributes to the increased risk?
Post fracture synovial fluid environment
Most cases of ankle arthritis are posttraumatic. Recent research has focused on the synovial fluid environment in the ankle after intra-articular fracture. After injury, an increase in proinflammatory cytokines and matrix metalloproteinases occurs that can lead to degradation of the cartilage. Intra-articular lavage has been proposed as a possible protective intervention to reduce the incidence of posttraumatic ankle arthritis.
Patient nonadherence with postoperative restrictions is frustrating and can increase the risk of postoperative complications, but this factor alone has not been demonstrated to be a risk factor for posttraumatic arthritis unless it leads to a loss of fixation. Inflammatory reactions to instrumentation are rare and have not been associated with posttraumatic arthritis. Prolonged postoperative immobilization can be associated with stiffness of the ankle joint but has not been shown to increase the risk of posttraumatic arthritis.
What is the osteoclast cell of origin?
Monocyte
Osteoclasts are of monocytic lymphocyte origin with the macrophage differentiation pathway. Although osteoclasts are derived from the hematopoietic lineage, osteoblasts are derived from mesenchymal stem cells. Osteoclast formation requires the presence of receptor activator of nuclear factor kappa-B ligand and macrophage colony-stimulating factor. These membrane-bound proteins are produced by neighboring stromal cells and osteoblasts, thus necessitating direct contact between these cells and osteoclast precursors.
When performing an arthroscopic release of the rotator interval for adhesive capsulitis, what ligament must be visualized to ensure the adequate depth of the rotator interval resection?
Coracoacromial
During the arthroscopic release of the rotator interval, it is important to resect the entire depth of the interval for complete release. The arthroscopic landmark for the complete release of the rotator interval is the visualization of the coracoacromial ligament superficially. The coracohumeral ligament and the superior and middle glenohumeral ligaments are anatomic components of the rotator interval.
A 20-year old amateur boxer has a 4-week history of snapping in his nondominant middle finger. He states that after it happens, he needs to use his opposite hand to extend his finger. He has tried taping his hands tighter, and he recently decreased his workouts, but the snapping persists. On examination, the finger “locks” in metacarpophalangeal (MP) joint flexion, although he can still extend the interphalangeal (IP) joints. Initial treatment should consist of
The boxer has a subacute tear of the sagittal band to his middle finger cause by repetitive blunt trauma to the dorsal MP joint. The middle finger is most commonly affected. The extensor tendon dislocates in the opposite direction of the tear. This injury can be distinguished by extensor tendon disruption displayed by the patient’s ability to maintain MP joint extension against resistance when the digit is extended and the tendon returns to its dorsal position. Up to 6 weeks, acute injuries can be treated with MP extension splints allowing IP flexion. Proximal IP (PIP) joint extension splinting may be appropriate for acute central slip disruption. The other options are appropriate for trigger finger, resulting in the finger locking in PIP joint flexion.
A 55-year-old man reports progressive left thigh pain. He has a history notable for renal cell carcinoma, for which he underwent a nephrectomy. He has radiographic evidence of a solitary lesion within the diaphysis of the left femoral shaft that is substantially thinning the cortices. The lesion was recently biopsied using a CT-guided core-needle technique; histology shows metastatic renal cell carcinoma. No other sites of disease are noted. What is the best next step?
This patient presents with a symptomatic solitary metastatic focus of renal cell carcinoma. Systemic therapy may be relevant, but observation does not offer improvement in local control, fracture prevention, or overall survival. Although prophylactic intramedullary nail fixation can indeed augment the bone in the short-term, it does not provide oncologic benefits and, moreover, may disseminate the tumor along the length of the entire long bone. This possibility makes subsequent management much more challenging and morbid and may obviate the ability to locally control the disease entirely. Curettage and packing does debulk the metastasis and augment bone strength but is unlikely to yield complete metastasectomy, and residual microscopic disease is likely. An intralesional procedure is also likely to result in substantial intraoperative bleeding, given the extremely vascular nature of renal cell carcinoma. En block excision and reconstruction offers the oncologic benefits of robust local control and improved cancer-specific survival. It also provides pain relief and fracture prevention.
What injury variable is associated with early conversion to total hip arthroplasty after the treatment of acetabular fractures?
Tannast and associates found a cumulative survival rate of 79% after a 20-year follow-up in patients with acetabular fractures who were surgically managed. A femoral head cartilage lesion was an independent negative prognostic factor favoring an early arthroplasty option. Other predictors were nonanatomical fracture reduction, age over 40 years, anterior hip dislocation, postoperative incongruence of the acetabular roof, involvement of the posterior acetabular wall, acetabular impaction, an initial displacement of the articular surface of 20 mm or more, and use of the extended iliofemoral approach. Routt and associates showed, in a review of surgically treated posterior wall acetabular fracture, that posterior wall comminution was not associated with an increased risk of conversion to total hip arthroplasty if reduction resulted in less than 1 mm of diastasis or step-off.
Ductile materials, such as metals and many polymers, exhibit plastic deformation before final failure. The inflection point from a linear to a nonlinear stress-strain response curve corresponds to the
If a metal rod is subjected to ever increasing loads, local failure will begin at microscopic defects in the material. These defects grow as the load increases. If the metal rod is subsequently unloaded, the deformation will be permanent. The inelastic part of the deformation is called plastic deformation. The transition point between elastic and plastic deformation is called the yield point, and it is associated with a corresponding yield stress. Some materials, such as ceramics, have brittle behavior with little or no plastic deformation; instead, a linear stress-strain response is present until failure occurs. Materials such as metals and many polymers exhibit extensive plastic deformation before final failure. In these ductile materials, an inflection point from a linear stress-strain response corresponds to the yield stress. If loading continues beyond the yield point, a maximum stress, called the tensile or ultimate strength, is reached.
A 21-year-old collegiate football lineman complains of right shoulder pain. He notices it mostly during blocking drills and bench presses and does not recall a specific traumatic incident. On examination, his shoulder has full painless range of motion and full external rotation strength in the neutral and abducted positions. He has negative Speed and O’Brien tests, a negative apprehension sign, and positive jerk and Kim tests. What is the most likely injured structure?
Posterior labrum
Posterior instability and labral injuries typically present with deep pain in the posterior shoulder region and this pain is exacerbated during activities with the arm in a flexed, adducted, and internally rotated position. This patient’s examination suggests a posterior labral injury. In his age and activity group, a rotator cuff injury is uncommon, and anterior instability or a SLAP/biceps lesion is not suggested from the question or the examination findings.
In an untreated chronic scapholunate dissociation, chondral degenerative changes initially occur most commonly at which articulation?
Stage I of scapholunate advanced collapse (SLAC) is characterized by the presence of radioscaphoid arthritis. A predictable pattern of the progression of degenerative changes for SLAC wrist occurs, including stage I (radial styloid involvement at the scaphoid fossa), stage II (scaphoid and entire scaphoid facet involvement), stage III (degeneration between the capitate and the lunate), and stage IV (pancarpal involvement). The radiolunate joint is often spared.
Anti-receptor activator of nuclear factor-κB ligand (anti-RANKL) therapy is currently pursued for the treatment of what type of bone tumor?
GCT
Giant cell tumor of bone is a rare, locally aggressive tumor that typically occurs in the bones of skeletally mature young adults in their second to fourth decades. Traditionally, surgery has been the mainstay of therapy for this disease, but the disease can recur even with optimal procedures. Furthermore, it may occur in locations where a surgical approach would be morbid. The maturation of the understanding of the role of the receptor activator of nuclear factor-κB ligand (RANKL) in the pathophysiology of giant cell tumor of bone has led to the use of denosumab, a monoclonal antibody against RANKL, in this disease. In 2013, the U.S. Food and Drug Administration approved denosumab for use in patients with recurrent, unresectable, or metastatic giant cell tumor of bone or in patients in whom surgery would be morbid.