by: Carol Frey, M.D.,• Keith S. Feder,•• and Christopher DiGiovanni,•••
Manhattan Beach, California, and Providence, Rhode lsland
This is a retrospective review of 49 subtalar arthrosco- pies performed between 1989 and 1996. Patients were evaluated in the following areas: (1) preoperative diag- nosis, (2) preoperative tests and clinical evaluation, (3) intraoperative findings, (4) postoperative diagnosis,(5) complications, and (6) clinical outcome. Particular atten- tion was paid to the accuracy of the preoperative diag- nosis, subtalar instability, intraoperative findings in sinus tarsi syndrome, and clinical outcome. Overall, this study demonstrated a success rate of 94o/o good and excellent results in the treatment of various types of subtalar pathologic conditions with arthroscopic techniques. The Workers’ Compensation cases reported 907o good and excellent results. The complication rate was low, with five minor complications reported. The most common complication was a trans¡ent neuropraxia involving branches of the supedicial peroneal nerve.
Of the 14 feet that had a preoperative diagnosis of sinus tarsi syndrome, all the diagnoses were changed at the time of arthroscopy. The postoperative diagnoses included 10 interosseous ligament tears, two cases of arthrofibrosis, and two degenerative joints. Based on these findings, “sinus tarsi syndrome” seems to be an inaccurate term that should be replaced with a specific diagnosis. Arthroscopy is the tool that will allow the orthopaedic surgeon to make a more accurate diagnosis.
The complex anatomy of the subtalar joint makes radiographic and arthroscopic examination difficult (3,5-8,11-14,16) (Fig. 1). With the introduction of small instruments and precise techniques, arthroscopy of the small joints, including the subtalar joint, has expanded during the last decade. Despite an expansion of techniques, the number of reports dealing with subtalar joint arthroscopy remains small, and even fewer reports deal with clinical applications and results.
The purpose of this study was to undertake a ret- rospective review of 49 subtalar arthroscopies per- formed by the senior author between 1989 and 1996. Patients were evaluated in the following areas: (‘1) preoperative diagnosis, (2) preoperative tests and clln- ical evaluation (including MRI and stress tests), (3) intraoperative findings, (4) postoperative diagnosis, (5) complrcations, and (6) clinical outcome. Particular at- tention was paid to the accuracy of preoperative di- agnosis, subtalar instability, intraoperative findings in sinus tarsi syndrome, and clinical outcome.
MATERIALS AND METHODS
A retrospective review was performed of all patients who had undergone subtalar arthroscopy between 1989 and 1996. lnclusion criteria for the study in- cluded having had a subtalar arthroscopy by the pri- mary author (C.C.F.) as well as adequate postopera- tive follow-up. A total of 45 patients (49 subtalar arthroscopies) made up the study population. For each patient, the preoperative diagnoses, operative findings, postoperative diagnoses, and outcome were recorded. This information was obtained from a review of initial histories and physicals, operative reports, office notes from follow-up visits, and radrographic studies (plain films, bone scans, magnetic resonance imaging (MRl), and computed tomography scans). ln 2’1 of 35 ankles that had stress radiographs of the ankle, the subtalar joint was also visualized. lnstability of the subtalar joint was assessed from the anterior drawer view when there was anterior translation of the posterior facet of the calcaneus on the talus. On the varus stress view, subtalar instability was indicated when a loss of parallelism was noted of the posterior facet of the calcaneus and the talus.a All perioperative complicat¡ons were noted. Any additional procedures performed at the time of surgery were also recorded.
The arthroscopic technique followed the initial de- scription of Parisien.ll’12 4n anterior, posterior, and middle portal were used. The middle poftal is essential for the evaluation of the sinus tarsi and its contents.s Local, general, spinal, or epidural anesthesia were used for this procedure. The patient was placed in the lateral decubitus position with the operative extremity up (Fig. 2A & B ). ln addition to padding between the legs, a bolster was placed distally under the operative extremity to suspend the foot and the leg. A tourniquet was used for hemostasis.
The three portals were available for visualization and instrumentation of the subtalar joint. The anterior portal was placed 2 cm anterior and 1cm distal to the tip of the lateral malleolus. The posterior portal was placed I cm proximal to the tip of the fibula and ante- rior to the Achilles tendon. The middle portal was placed under direct visualization, using an 1B-gauge needle with outside-in technique. A 2.7-mm 30″ oblique arthroscope and an arthroscopic pump were used for the procedure.
The overall demographics of this patient group were as follows. The average age was 35 years (range, 17-66). There were 26 men and 19 women. Twenty- eight (57%) of the subtalar joints involved Workers’ Compensation cases, and 21 (43%) did not. The mechanism of injury was a twisting injury to the foot and ankle (usually inversion) in 32 feet (62%), direcT blow or crush injury in 10 feet (21%), overuse injury (such as climbing or walking on uneven ground) in five feet (12Yo), and congenital (fibrous coalition) in two feet (5%). The average follow-up was 54 months (12-BB months). No patient who entered into the study was lost to follow-up.
Preoperatively, the diagnoses included interosse- ous ligament injury in 26 feet (53%), sinus tarsi syn- drome in 14 feet (25%), fibrous coalition in four feet (B%), ar|hrofibrosis in three feel (6%), and osteochon- dral fracture of the posterior subtalar joint in two feet (4%). Diagnosis of sinus tarsi syndrome was made on primarily subjective findings that included pain over the sinus tarsi, feelings of instability in the hindfoot, and pain relief after injection of local anesthetic into the sinus tarsi.10 The MRI in sinus tarsi syndrome may show findings consistent with scar, ganglion cyst, or interosseous ligament disruption. The diagnosis of in- terosseous ligament injury was made when the same subjective findings were present as in sinus tarsi syn- drome, but in addition, the MRI showed disruption of the interosseous ligament. The interosseous ligaments are seen best on sagittal and coronal views. lt should be noted that the diagnosis of interosseous ligament tears were made in later cases after the radiologist and the surgeon had gained more experience in reading the MRls and comparing ihem to intraoperative find- ings. Only one case of interosseous ligament injury was noted to have instability of the subtalar joint, preoperatively, as demonstrated by stress views of the subtalar joint (Fig. 3).
Fibrous coalition was a diagnosis based on the presence of a subtalar joint with limited range of mo- tion but not after trauma or long term immobilization. MRI findings were suggestive for a fibrous coalition. ln addition, x-rays showed either a squaring off of the borders of the calcaneonavicular articulation on an oblique view of the foot or an obliquity of the medial facet of the subtalar joint on Harris vìews. Arthrofibro- sis was a diagnosis based on the clinical findings of a joint with limited range of motion, which usually existed after trauma or immobilization. The patients with arthrofibrosis dìd not have findings on MRI or x-rays to suggest a tarsal coalition.
Postoperatively, the following diagnoses were made: interosseous ligament injury in 36 feet (74%), arthrofibrosis in seven feet (14%o), degenerative joint disease in four feet (B%), and fibrous coalition of the calcaneonavicular joint in two feel (4%). Of the 36 feet with interosseous ligament tears, 27 feet demon- strated scar formation and gross hyalinization of the torn ligament ends and subsequent impingement of this material into the anterior aspect of the posterior subtalar joint. This is referred to by the authors as the subtalar impingement lesion (STIL) (Fig. a).
Postoperatively, the diagnosis was changed or clar- ified in 17 feet (35%). The diagnosìs was changed postoperatively in all cases of sinus tarsi syndrome, in all cases of osteochondral fractures, and in two cases of fibrous coalition.
Of the 14 feet that had a preoperative diagnosis of sinus tarsi syndrome, the following postoperative di- agnoses were made: interosseous ligament tear in 10 feet, arthrofibrosis in two feet, and degenerative joint disease in two feet.
Of the 36 cases that demonslrated injury to the interosseous ligaments, only one case demonstrated instability by stress radiographs, preoperatively. lntra- operatively, seven feet demonstrated subtalar insta- bility; six of these feet had a 75% tear of the interosseous ligament and one had a complete tear. lt should be noted, again, that althor-rgh seven cases demon- strated subtalar instability, intraoperatively, only one demonstrated instability on preoperative stress radio- graphs. l-lowever, of 29 feel wittrout clemonstrable subtalar instability, the following extent of injury was documented: three had a 25% lear, 17 had a 50%.