ABSTRACT
BACKGROUND: Intraneural cysts involving the tibial nerve in the knee region (popliteal fossa) are rare. According to the articular (synovial) theory, which posits a joint origin for this pathology, these cysts originate from either the superior tibiofibular joint (STFJ) or the tibiofemoral (knee) joint. As tibial intraneural cysts arising from the tibiofemoral joint remain poorly understood, the authors present 2 illustrative cases and a review of the world's literature on all tibial intraneural ganglion cysts in the knee region. OBSERVATIONS: Fourteen cases of tibial intraneural ganglion cysts arising from the tibiofemoral joint were identified in the literature. Different articular branch patterns were demonstrated, which could be explained by the varied, rich articular branch innervation at the knee. Favorable outcomes were observed in cases in which the articular branch had been disconnected and the cyst drained and were comparable to the outcomes seen in tibial intraneural ganglion cysts with an STFJ origin. LESSONS: Tibial intraneural cysts in the knee region can be subdivided by their joint of origin: the STFJ or the tibiofemoral joint. Those arising from the tibiofemoral joint originate from different areas of the joint and propagate in predictable patterns, with favorable outcomes following surgical intervention when the joint connection is identified and treated. The origin of tibial intraneural cysts from the tibiofemoral joint are more complex than those originating from the STFJ but seem to have similar propagation patterns and outcomes.
ABSTRACT
BACKGROUND: Intraneural ganglion cysts involving the tibial nerve are rare. Recent evidence has supported an articular (synovial) theory to explain the joint-related origin of these cysts; however, optimal operative treatment for cysts originating from the STFJ remains poorly understood. Therefore, we present a novel strategy: addressing the joint itself without addressing the articular branch and/or the cyst. METHODS: Records of patients with tibial intraneural ganglion cysts with a connection to the STFJ who were treated with a joint resection alone at a single academic institution were reviewed. The clinicoradiographic features, operative intervention, and postoperative course were recorded. RESULTS: We identified a consecutive series of 7 patients. These patients (4/7 male, 57%) were 43 (range 34-61) years of age and all presented with symptoms of neuropathy. The patients underwent resection of the synovial surfaces of the STFJ without disconnection of the articular branch or decompression of the cyst. Postoperatively, three patients regained partial motor function (43%, n=7), although four patients noted continued sensory abnormality (57%, 4/7). All six patients with postoperative MRIs had some evidence of regression of the cyst. CONCLUSIONS: This novel surgical technique serves as a proof of concept-highlighting the fact that treating the primary source (the joint origin) can be effective in eliminating the secondary problem (the cyst itself). While this study shows that this simplified approach can be employed in select cases, we believe that superior results (faster, fuller recovery) can be achieved with combinations of disconnecting the articular branch, decompressing the cyst, and/or resecting the joint.
Subject(s)
Ganglion Cysts , Humans , Male , Ganglion Cysts/diagnostic imaging , Ganglion Cysts/surgery , Knee Joint/diagnostic imaging , Knee Joint/surgery , Tibial Nerve/diagnostic imaging , Tibial Nerve/surgery , Magnetic Resonance Imaging/methods , Postoperative PeriodABSTRACT
BACKGROUND: Advancements in imaging and an understanding of the pathomechanism for intraneural ganglion cyst formation have led to increased awareness and recognition of this lesion. However, the precise role of imaging has been advocated for but not formally evaluated. METHODS: We performed a systematic review of the world literature to study the frequency of imaging used to diagnose intraneural ganglion cysts at different sites and compared trends in identifying joint connections. RESULTS: We identified 941 cases of intraneural ganglion cysts, of which 673 had published imaging. Magnetic resonance imaging (MRI, n = 527) and ultrasonography (US, n = 123) were the most commonly reported. They occurred most frequently in the common peroneal nerve (n = 570), followed by the ulnar nerve at the elbow (n = 88), and the tibial nerve at the ankle (n = 58). A joint connection was identified in 375 cases (48%), with 62% of MRIs showing a joint connection, followed by 16% on US, and 6% on computed tomography (CT). MRI was statistically more likely to identify a joint connection than was US (P < 0.01). In the last decade, joint connections have been identified with increasing frequency using preoperative imaging, with up to 75% of cases reporting joint connections. CONCLUSIONS: Preoperative imaging plays an important role in establishing the diagnosis of intraneural ganglion cyst as well as treatment planning. Imaging has proved superior to the sole reliance of operative exposure to identify a joint connection, which is necessary to treat the underlying disease. Failure to identify cyst connections on imaging can result in an inability to truly address the underlying pathoanatomy at the time of definitive surgery, leading to a risk for clinical recurrence. Therefore, management should be guided by an intersection between new knowledge presented in the literature, clinical expertise, and surgeon experience.
Subject(s)
Ganglion Cysts , Ganglia/pathology , Ganglion Cysts/diagnostic imaging , Ganglion Cysts/surgery , Humans , Magnetic Resonance Imaging/methods , Peroneal Nerve/diagnostic imaging , Peroneal Nerve/pathology , Tibial Nerve/pathologyABSTRACT
Femoral de-rotation osteotomy (FDO) and hip arthroscopy are both recognized surgical options for the management of femoroacetabular impingement (FAI) in the setting of decreased femoral anteversion (<5°). Minimal comparative data exist regarding the difference in outcomes between these two techniques, and we believe this is the first study to provide that comparison. This retrospective cohort study included a total of 20 patients with such pathology, matched for age, gender and body mass index. A total of 10 patients were included in the FDO group [median anteversion -0.5° (true retroversion); average follow-up 17.9 months]. In total, 10 patients were included in the hip arthroscopy group [median anteversion -0.5° (true retroversion); average follow-up 28.5 months]. Both groups demonstrated statistically and clinically significant improvement in the post-operative International Hip Outcome Tool (iHOT-33) scores [median improvement: FDO group, 37.7 points (r 14-58.8; P < 0.041); hip arthroscopy group, 35.9 points (r 11.1-81; P < 0.05)], noting that the minimal clinically important difference for the iHOT-33 is 6.1 points. However, the study was not adequately powered to delineate a difference in improvement between the two groups. The findings suggest significant improvement in patient-reported outcomes, and clinical findings can be achieved with either FDO or hip arthroscopy for FAI in the setting of decreased femoral anteversion. However, selection of the most suitable surgical procedure using a patient-specific approach may optimize outcomes in this challenging population.
ABSTRACT
PURPOSE: The dynamic nature of intraneural ganglion cysts, including spontaneous expansion and regression, has been described. However, whether these cysts can regress completely in the absence of surgical management has important therapeutic implications. Therefore, we aim to review the literature for cyst regression without surgical intervention. METHODS: We reviewed our database of 970 intraneural ganglion cysts in the literature to search for evidence of complete regression based on strict radiologic confirmation, either spontaneously, or after percutaneous cyst aspiration or steroid injection. RESULTS: We did not find any examples of complete regression without surgical treatment that met inclusion criteria. Spontaneous regression was reported in four cases; however, only two cases had follow-up imaging, both of which demonstrated residual cysts. Nineteen cases of percutaneous intervention were found in the literature, 13 of which reported clinical improvement following aspiration/steroid injection; however, only seven cases had available imaging. Only two cases reported complete resolution of cyst on MR imaging at follow-up, but reinterpretation found residual intraneural cyst in both cases. CONCLUSION: We believe that pathology (structural abnormalities and/or increased joint fluid) always exists at the joint origin of intraneural ganglion cysts which persist even with regression of the cyst. The persistence of a capsular abnormality or defect can lead to recurrence of the cyst in the future, and while imaging may show dramatic decreases in cyst size, truly focused assessment of images will show a tiny focus of persistent intraneural cyst at the joint origin. Thus, expectant management or percutaneous intervention may lead to regression, but not complete resolution, of intraneural ganglion cysts.
Subject(s)
Ganglion Cysts , Ganglion Cysts/diagnostic imaging , Ganglion Cysts/pathology , Ganglion Cysts/surgery , Humans , Magnetic Resonance Imaging/methods , Retrospective Studies , SteroidsSubject(s)
Ganglion Cysts , Ganglion Cysts/diagnostic imaging , Humans , Magnetic Resonance Imaging , Tibial NerveSubject(s)
Arthritis, Infectious , Arthroplasty, Replacement, Hip , Arthroplasty, Replacement, Knee , Prosthesis-Related Infections , Arthroplasty, Replacement, Hip/adverse effects , Arthroplasty, Replacement, Knee/adverse effects , Humans , Prosthesis-Related Infections/diagnosis , Prosthesis-Related Infections/prevention & control , Prosthesis-Related Infections/surgery , VancomycinABSTRACT
BACKGROUND: Periprosthetic joint infection (PJI) after hip and knee arthroplasty is a leading cause of revision surgery, inferior function, complications, and death. The administration of topical, intrawound vancomycin (vancomycin powder) has appeared promising in some studies, but others have found it ineffective in reducing infection risk; for that reason, a high-quality systematic review of the best-available evidence is needed. QUESTIONS/PURPOSES: In this systematic review, we asked: (1) Does topical vancomycin (vancomycin powder) reduce PJI risk in hip and knee arthroplasty? (2) Does topical vancomycin lead to an increased risk of complications after hip and knee arthroplasty? METHODS: A search of Embase, MEDLINE, and PubMed databases as of June 2020 was performed according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. Studies comparing topical vancomycin in addition to standard infection prevention regimens (such as routine perioperative intravenous antibiotics) with standard regimens only in primary hip and knee arthroplasty were identified. Patients 18 years or older with a minimum follow-up of 3 months were included. No restrictions on maximal loss to follow-up or PJI definition were imposed. Studies were excluded if they included patients with a history of septic arthritis, used an antibiotic other than vancomycin or a different route of administration for the intervention, performed additional interventions that differed between groups, or omitted a control group. A total of 2408 studies were screened, resulting in nine eligible studies reviewing 3371 patients who received topical vancomycin (vancomycin powder) during a primary THA or TKA and 2884 patients who did not receive it. Groups were comparable with respect to duration of follow-up and loss to follow-up when reported. Study quality was assessed using the Newcastle-Ottawa scale, showing moderate-to-high quality for the included studies. The risks of PJI and overall complications in the topical vancomycin group were compared with those in the control group. RESULTS: One of nine studies found a lower risk of PJI after primary THA or TKA, while eight did not, with odds ratios that broadly bracketed the line of no difference (range of odds ratios across the nine studies 0.09 to 1.97). In the six studies where overall complications could be compared between topical vancomycin and control groups in primary THA or TKA, there was no difference in overall complication risks with vancomycin (range of ORs across the six studies 0.48 to 0.94); however, we caution that these studies were underpowered to detect differences in the types of uncommon complications associated with vancomycin use (such as allergy, ototoxicity, and nephrotoxicity). CONCLUSION: In the absence of clear evidence of efficacy, and without a sufficiently large evidence base reporting on safety-related endpoints, topical vancomycin (vancomycin powder) should not be used in routine primary THA and TKA. Adequately powered, multicenter, prospective trials demonstrating clear reductions in infection risk and large registry-driven audits of safety-related endpoints are required before the widespread use of topical vancomycin can be recommended. LEVEL OF EVIDENCE: Level III, therapeutic study.
Subject(s)
Antibiotic Prophylaxis/methods , Arthroplasty, Replacement, Hip/adverse effects , Arthroplasty, Replacement, Knee/adverse effects , Joint Prosthesis/microbiology , Prosthesis-Related Infections/prevention & control , Vancomycin/administration & dosage , Administration, Topical , Adult , Aged , Female , Humans , Joint Prosthesis/adverse effects , Male , Middle Aged , Treatment OutcomeABSTRACT
CASE: A healthy 36-year-old man developed compartment syndrome of the posterior thigh with an associated sciatic nerve palsy secondary to an acute proximal hamstring tendon avulsion injury. CONCLUSION: Compartment syndrome of the thigh is rare and is usually associated with high-energy trauma. Atraumatic causes have been described, typically involving the anterior compartment. Posterior thigh compartment syndrome is especially uncommon. This case highlights the potential occurrence of posterior thigh compartment syndrome after proximal hamstring tendon rupture. Given the morbidity associated with compartment syndrome, it is important to recognize the risk factors and injury patterns that can cause thigh compartment syndrome.
Subject(s)
Compartment Syndromes/etiology , Fasciotomy , Hamstring Tendons/injuries , Tendon Injuries/complications , Adult , Compartment Syndromes/surgery , Humans , Male , Negative-Pressure Wound Therapy , Tendon Injuries/surgeryABSTRACT
BACKGROUND: Surgical fixation of tibial plateau fracture in elderly patients with open reduction and internal fixation (ORIF) provides inferior outcomes compared with younger patients. Primary total knee arthroplasty (TKA) may be of benefit in elderly patients with a combination of osteoporotic bone and metaphyseal comminution. However, there continues to be conflicting evidence on the use of TKA for primary treatment of tibial plateau fracture. This systematic review was performed to quantify the outcomes and perioperative complication rates of TKA for primary treatment of tibial plateau fracture. MATERIALS AND METHODS: A comprehensive search of MEDLINE, Embase, and PubMed databases from inception through March 2018 was performed in accordance with PRISMA guidelines. Two reviewers independently screened papers for inclusion and identified studies featuring perioperative complications and outcomes of primary TKA for tibial plateau fracture. Weighted means and standard deviations are presented for each outcome. RESULTS: Seven articles (105 patients) were eligible for inclusion. All-cause mortality was 4.75 ± 4.85%. The total complication rate was 15.2 ± 17.3%. Regarding outcomes, Knee Society scores were most commonly reported. The average Knee Society Knee Score was 85.6 ± 5.5, while the average Knee Society Function Score was 64.6 ± 13.7. Average range of motion at final follow-up was 107.5 ± 10.0°. CONCLUSIONS: Primary TKA for select tibial plateau fractures has acceptable clinical outcomes but does not appear to be superior to ORIF. It may be appropriate to treat certain geriatric patients with TKA to allow for early mobilization and reduce the need for reoperation. Other factors may need to be considered in deciding the optimal treatment. LEVEL OF EVIDENCE: Level III.
Subject(s)
Arthroplasty, Replacement, Knee , Knee Injuries/surgery , Knee Joint/surgery , Tibial Fractures/surgery , Arthroplasty, Replacement, Knee/adverse effects , HumansABSTRACT
CASE: We present the unique case of deltoid and hand compartment syndrome in a young man after prolonged syncope because of polysubstance use. The patient was subsequently treated with urgent deltoid and hand compartment fasciotomies which resulted in full recovery of his shoulder function. CONCLUSIONS: Patients suspected of deltoid compartment syndrome should have a thorough physical examination, followed by repeat examinations. Invasive compartment monitoring should be used in equivocal cases, in patients with decreased level of consciousness, and in patients with distracting injury. Once diagnosed, deltoid compartment syndrome (± other compartments) should be taken for emergent fasciotomy, ensuring adequate decompression of all 3 deltoid compartments.
Subject(s)
Compartment Syndromes/surgery , Deltoid Muscle/surgery , Fasciotomy/methods , Hand/surgery , Syncope/complications , Adult , Compartment Syndromes/etiology , Humans , Male , Substance-Related Disorders/complications , Syncope/chemically inducedABSTRACT
Superficial radial intraneural ganglion cysts are rare. Only nine previous cases have been described. We provide two examples with a wrist joint connection and review the literature to provide further support for the unifying articular (synovial) theory for the pathogenesis and treatment of intraneural ganglia.
Subject(s)
Ganglion Cysts/surgery , Wrist/surgery , Adult , Female , Ganglion Cysts/diagnostic imaging , Ganglion Cysts/pathology , Humans , Magnetic Resonance Imaging , Male , Wrist/diagnostic imaging , Wrist/pathologyABSTRACT
BACKGROUND: Redislocation of the native hip is rare. An anterior fulcrum between the proximal part of the femur and the pelvis must be present for a posterior dislocation to occur. The purpose of this study is to describe the cases of 9 patients with posterior redislocation or recurrent subluxation of the native hip that was treated with hip preservation surgery. METHODS: We retrospectively identified the cases of 9 patients, from 2 institutions, who had undergone hip preservation surgery for the management of posterior redislocation or recurrent subluxation of the native hip after a dislocation. The mean number of dislocations prior to surgery was 3.2 (range, 1 to 7). Pelvic radiographs were used to classify the acetabular morphology, sufficiency of acetabular containment, and structural anatomy of the proximal part of the femur. Radiographic identification of impinging structures was used to guide surgical treatment, which involved either femoral correction alone or the combination of femoral correction and an anteverting periacetabular osteotomy. RESULTS: At a mean follow-up of 73.8 months (range, 10 to 192 months), there had been no subsequent episodes of dislocation or subluxation in any of the hips treated with correction of the anatomic pivot point. An algorithmic approach is presented. CONCLUSIONS: In patients who have episodes of redislocation or recurrent subluxation of the native hip, the identification of anatomic abnormalities that create a fulcrum between the proximal part of the femur and the pelvis is critical for making appropriate treatment decisions. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Subject(s)
Acetabulum , Femur , Hip Dislocation/surgery , Acetabulum/anatomy & histology , Acetabulum/surgery , Algorithms , Femur/anatomy & histology , Femur/surgery , Follow-Up Studies , Hip Dislocation/pathology , Hip Joint/anatomy & histology , Hip Joint/surgery , Humans , Recurrence , Retrospective StudiesABSTRACT
Osteochondral defects of the femoral head are rare. Several treatment options have been described, though there is currently no consensus on the appropriate management of these lesions. Five patients underwent femoral head osteochondral autograft transfer for treatment of ipsilateral femoral head osteochondral defects via surgical hip dislocation between 2011 and 2014 at our institution. The mean age of the patients was 24.8 (16-37) years. There were four females and one male. Mean follow-up was 53.8 (30-64) months. Four patients reported complete resolution of preoperative pain, return to baseline activities and were satisfied with their results. Harris hip scores improved from a mean 60.8 (30-87) to 86.6 (44-100). There was no radiographic evidence of progression of the femoral head defects. There were no operative complications. Osteochondral autograft transfer from the ipsilateral femoral head using a surgical hip dislocation demonstrated good clinical and radiographic outcomes at midterm follow-up in our cohort and may be considered a suitable option for management of these lesions in select patients. Further research and follow-up is warranted to more clearly define the indications and outcomes of this procedure.
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BACKGROUND: Metaphyseal fixation has promising early results in providing component stability and fixation in revision total knee arthroplasty (TKA). However, there are limited studies on midterm results of metaphyseal sleeves. We analyzed complications, rerevisions, and survivorship free of revision for aseptic loosening of metaphyseal sleeves in revision TKA. METHODS: Two hundred eighty patients with 393 metaphyseal sleeves (144 femoral, 249 tibial) implanted during revision TKA from 2006-2014 were reviewed. Sleeves were most commonly cemented (55% femoral, 72% tibial). Mean follow-up was 3 years, mean age was 66 years, and mean body mass index was 34 kg/m2. Indications for revision TKA included 2-stage reimplantation for deep infection (37%), aseptic loosening of the tibia (14%), femur (12%), or both components (9%), and instability (14%). RESULTS: There was a 12% rate of perioperative complications, most commonly intraoperative fracture (6.5%). Eight sleeves (2.5%) required removal: 6 (2%) during component resection for deep infection (all were well-fixed at removal) as well as 1 (0.8%) femoral sleeve and 1 (0.8%) tibial sleeve for aseptic loosening. Five-year survivorship free of revision for aseptic loosening was 96% and 99.5% for femoral and tibial sleeves, respectively. Level of constraint, bone loss, sleeve and/or stem fixation, and revision indication did not significantly affect outcomes. CONCLUSION: Metaphyseal sleeve fixation to enhance component stability during revision TKA has a 5-year survivorship free of revision for aseptic loosening of 96% and 99.5% in femoral and tibial sleeves, respectively. Both cemented and cementless sleeve fixation provides reliable durability at intermediate follow-up.
Subject(s)
Arthroplasty, Replacement, Knee/instrumentation , Knee Prosthesis , Adult , Aged , Aged, 80 and over , Female , Femur/surgery , Humans , Knee Joint/surgery , Male , Middle Aged , Prosthesis Design , Prosthesis Failure , Reoperation , Tibia/surgeryABSTRACT
BACKGROUND: The Exeter cemented femoral stem has demonstrated excellent clinical and radiographic outcomes as well as long-term survivorship free from aseptic loosening. A shorter revision stem (125 mm) with a 44 offset became available for the purpose of cement-in-cement revision situations. In certain cases, this shorter revision stem may be used for various primary total hip arthroplasties (THAs) where the standard length stem would require distally reaming the femoral canal. We sought to report on the early to midterm results of this specific stem when used for primary THA regarding (1) clinical and radiographic outcomes, (2) complications, and (3) survivorship. METHODS: Twenty-nine patients (33 hips) underwent a hybrid THA using the smaller revision Exeter cemented femoral stem. Twenty-five patients (28 hips) had at least 2 years of follow-up and were assessed for clinical and radiographic outcomes. All 33 hips were included in the analysis of complications and survivorship. The Kaplan-Meier survivorship was performed using revision for all causes and for aseptic loosening as the end points. RESULTS: The average clinical follow-up was 4 years (range, 2-7). Harris Hip Scores improved from a mean preoperative value of 56 (range, 23-96) to 90 (range, 51-100) at the latest follow-up. All patients demonstrated superior cement mantles with no signs of loosening. One patient suffered a B2 periprosthetic fracture and 1 patient experienced 2 episodes of instability. The 5-year Kaplan-Meier survivorship was 96.7% for all causes of revision and was 100% using aseptic loosening as the end point. CONCLUSION: The shorter Exeter revision cemented femoral stem has favorable early to midterm clinical and radiographic outcomes when used for primary THA with a low complication rate and is a viable option in patients with narrow femoral canals where uncemented stem fixation is not desired.
Subject(s)
Arthroplasty, Replacement, Hip/instrumentation , Hip Prosthesis/statistics & numerical data , Adult , Aged , Aged, 80 and over , Bone Cements , Female , Femur/surgery , Follow-Up Studies , Humans , Male , Middle Aged , Prosthesis Design , Prosthesis Failure , Reoperation/instrumentation , Retrospective Studies , Treatment OutcomeABSTRACT
OBJECTIVES: To define the incidence, risk factors, and anatomic location of articular malreductions in operatively treated lateral tibial plateau fractures. DESIGN: Prospective Cohort Study. SETTING: Academic Level 1 Trauma Centre. PATIENTS/PARTICIPANTS: Study subjects were patients entered into a prospective cohort study of tibial plateau fractures. INTERVENTIONS: Surgical fixation of tibial plateau fractures and postoperative computed tomographies (CTs). MAIN OUTCOME MEASURES: The primary outcome was incidence of articular malreduction. Secondary outcomes included risk factors for malreduction and a descriptive analysis of malreduction location. RESULTS: Sixty-five postoperative CTs were reviewed. Twenty-one reductions (32.3%) had a step or gap more than 2 mm. The frequency of malreductions in patients undergoing submeniscal arthrotomy or fluoroscopic-assisted reduction alone was 16.6% and 41.4%, respectively (P = 0.0021). Age, body mass index, OTA/AO fracture type, operative time, use of bone graft or bone graft substitute, and use of locking plates were not predictive of malreduction. Malreductions were heavily weighted to the posterior quadrants of the lateral tibial plateau. CONCLUSIONS: When examined using cross-sectional imaging the rate of articular malreductions was high at 32.3%. Fluoroscopic reduction alone was a predictor for articular malreduction. Most malreductions were located in the posterior quadrants of the lateral plateau. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
Subject(s)
Bone Transplantation/statistics & numerical data , Fracture Fixation, Internal/statistics & numerical data , Joint Instability/epidemiology , Postoperative Complications/epidemiology , Tibial Fractures/epidemiology , Tibial Fractures/surgery , Adult , Age Distribution , Aged , Canada/epidemiology , Causality , Cohort Studies , Comorbidity , Female , Humans , Incidence , Joint Instability/diagnosis , Joint Instability/prevention & control , Knee Injuries/diagnostic imaging , Knee Injuries/epidemiology , Knee Injuries/surgery , Male , Middle Aged , Postoperative Complications/diagnosis , Postoperative Complications/prevention & control , Prognosis , Risk Factors , Sex Distribution , Treatment OutcomeABSTRACT
Intraneural ganglion cysts in the tarsal tunnel are rare. We present a patient who had an intraneural ganglion cyst involving the medial and lateral plantar and distal tibial nerves. Magnetic resonance imaging revealed evidence to support the joint-related (i.e., subtalar) origin of the cyst. Careful reinterpretation of the imaging supported a phasic mechanism (i.e., cross-over) to explain the interrelated pathogenesis of the intraneural cyst within the three nerves. This mechanism is analogous to that described for the prototypes-the peroneal, tibial and sciatic nerves in the knee region-and can be generalized to other nerves in the foot and ankle region. We believe that understanding the pathogenesis sheds light on the effective treatment.