Lower leg muscle recovery takes at least 12 months for functional tests to recover after late reconstruction of the tibialis posterior tendon retinaculum

Abstract

Traumatic dislocation of the tibialis posterior tendon is an extremely rare injury with few reported cases. It is a complicated injury with high risk of misdiagnosis and mistreatment. MRI is the best tool for diagnosis. Surgical treatment has been reported to have a better outcome than conservative treatment. In the present case, a 23-year-old female athlete sustained a sports-related traumatic tibialis posterior tendon dislocation with retinaculum rupture. The patient underwent late reconstruction of the ruptured retinaculum followed by a personalised rehabilitation programme. Full recovery was achieved after 19 months according to European Foot and Ankle Society Score and Foot and Ankle Outcome Score. Lower leg muscle strength continued to improve until 6 months after surgery in isokinetic strength and physical performance tests.

Background

Traumatic dislocation of the tibialis posterior tendon is an extremely rare injury, with approximately 50 reported cases in the English literature.^1–7 The first case was reported by Martius after falling from a balloon in 1874.⁸ A twisting injury with plantar hyperflexion and inversion in the varus position of the ankle joint is the main mechanism for traumatic dislocation of the tibialis posterior tendon.^{3 7} In many cases, it is misdiagnosed as a typical ankle sprain and, therefore, mistreated. Swelling in acute cases and atypical pain in chronic cases are the main reasons for misdiagnosis^{3–5 9} Investigation via plain X-ray is suggested to rule out fractures. With active cooperation from the patient, ultrasound (US) is suggested to detect pathological changes in the region of the tibialis posterior tendon during manipulation of the tendon.¹⁰ MRI scans are useful to examine the position of the tibialis posterior tendon, tendon groove and the anatomy of the retinaculum.³ Surgical treatment is reported to be superior compared with conservative treatment. Several surgical techniques are described for anatomic repair or reconstruction of the tibialis posterior tendon retinaculum with or without additional procedures.3 5 7 11 12 Rehabilitation protocols include the use of an orthotic boot or cast immobilisation, followed by progressive weight bearing with restoration of ankle motion. A return to pivoting activities is not recommended before 6 months.² Case reports have reported successful treatment of patients from 6¹ up to 28¹³ months postoperatively.

To the knowledge of the authors, there are no reports in the literature of lower leg muscle recovery as measured by isokinetic strength tests together with subjective ankle scores after late surgical treatment of tibialis posterior tendon dislocation.

In the present case, a 23-year-old female athlete sustained a sports-related traumatic tibialis posterior tendon dislocation. She underwent surgical treatment, and her postoperative muscle strength and subjective evaluation were followed until full recovery.

Case presentation

A 23-year-old, physically very active, healthy, recreational female athlete sustained a trauma to her left ankle in November 2019 while skiing downhill. She felt immediate pain in the posterior side of the medial malleolus with visible swelling and haematoma. The first visit to the orthopaedic surgeon took place 2 months after the primary injury. The patient reported of pain in the posteromedial side of the tibia with the feeling that something was popping out during physical activity. There was no pain while at rest.

The clinical examination revealed a stable ankle joint in valgus, varus and a normal anterior drawer test. Attention focused on atypical posteromedial ankle symptoms. Palpation of the posteromedial side of the medial malleolus provoked localised pain together with anterior tendon dislocation of the tibialis posterior tendon (video 1.) No signs of vascular or neurologic deficits were seen.

Video 1.

bcr-2021-247273supp000.mp4 ^{(668.9KB, mp4)}

DOI: 10.1136/bcr-2021-247273.video01

A plain left ankle X-ray was obtained to rule out fractures. An MRI was obtained to image the position of the tibialis posterior tendon and the retinaculum, and to classify the type of rupture.

The patient was not initially ready for early surgical intervention for personal reasons. Therefore, an individual rehabilitation programme was initiated; however, the results were disappointing after 4 weeks. Consequently, surgical treatment was performed 4 months after the primary traumatic episode. A subperiosteal type of dislocation with a ruptured retinaculum of the tibialis posterior tendon was found, together with mild synovitis and a normal tendon groove.

Patient-reported outcome measurements (PROMs) were calculated at 2, 6, 12 and 19 months (table 1), and isokinetic muscle strength was measured at 6, 12 and 19 months postoperatively (table 2).

Table 1.

EFAS and FAOS results

Postoperative time	2 weeks	2 months	6 months	12 months	19 months
EFAS total (24 max)	12	16	19	23	24
EFAS sports (16 max)	4	2	11	14	15
FAOS total	73	74	92	90	99
FAOS symptoms	86	82	93	89	100
FAOS pain	81	78	92	92	100
FAOS ADL	85	84	100	100	100
FAOS sports	30	50	85	75	100
FAOS Qlife	38	44	69	69	94

ADL, activities of daily living; EFAS, European Foot and Ankle Society Score; FAOS, Foot and Ankle Outcome Score; Qlife, quality of life.

Table 2.

Isokinetic tests and physical performance tests in the injured and uninjured leg

Test	2 months OP	2 months NOP	6 months OP	6 months NOP	12 months OP	12 months NOP	19 months OP	19 months NOP
ISOK INV 30°/s (Nm)	x	x	19	24	49	43	31	41
ISOK EV 30°/s (Nm)	x	x	15	28	31	24	18	16
ISOK INV 120°/s (Nm)	x	x	14	16	30	33	24	27
ISOK EV 120°/s (Nm)	x	x	11	12	26	16	12	12
Y balance AR (cm)	x	x	62	72	70	72	71	71
Y balance PM (cm)	x	x	103	110	105	110	103	106
Y balance PL (cm)	x	x	95	103	103	104	100	101
Ankle lunge (cm)	10	15.5	15	15.5	15.5	15.5	14	14.5

ISOK EV, sokinetic test, eversion; ISOK INV, isokinetic test, inversion; NOP, non-operated leg; OP, operated leg; Y-balance AR, Y-balance test, anterior reach; Y-balance PL, Y-balance test, posterolateral reach; Y-balance PM, Y-balance test, posteromedial reach.

Investigations

Plain X-rays: typical AP and side view X-rays of the left ankle joint were taken. No signs of fractures or other pathological changes were found.

MRI: based on findings of clinical investigations, an MRI of the left ankle joint was ordered. In the axial view of the MRI scan, the tibialis posterior tendon location was medial to its usual anatomic position. Also, a ruptured retinaculum was found (figure 1). In the sagittal view, synovitis around the tibialis posterior tendon and non-anatomic localisation of the tibialis posterior tendon was found (figure 2).

Figure 1.

MRI of the left ankle joint shows dislocation of the tibialis posterior tendon and a retinaculum injury of the tendon sheath.

Figure 2.

MRI of the left ankle joint with synovitis around the tibialis posterior tendon and a retinaculum injury of the tendon sheath.

Differential diagnosis

Tibialis posterior tendon dislocation and rupture of the retinaculum are caused by a twisting injury with plantar hyperflexion and inversion in the varus position of the ankle joint during sporting activities or other high-energy accidents. Such an injury can be misdiagnosed as a typical ankle sprain or ligament injury because of swelling around the medial malleolus and ankle joint, which means it is not possible to palpate the tendon in acute cases; therefore, it may be mistreated. In chronic cases, it can also be difficult to diagnose, and the examiner needs to be experienced.

Treatment

Based on MRI findings, a traumatic tibialis posterior tendon dislocation was diagnosed, and surgical treatment was initiated due to failure of the conservative approach.

Surgical technique: spinal anaesthesia was used with the patient in the abdominal position. A thigh tourniquet was applied with a pressure of 350 mm Hg. A 5 cm posteromedial skin incision was made in the region of the posterior side of the medial malleolus. The retinaculum was dissected, and an unstable tibialis posterior tendon was exposed under the retinaculum. A 4 cm retinaculum incision was made approximately 1.5 cm medially to the footprint of the retinaculum. This initial surgical step revealed that the retinaculum was not attached to the footprint and the tibialis posterior tendon was able to dislocate medially. The tendon tissue was intact. The footprint of the retinaculum was debrided, and scar tissue was removed down to the cortical bone. Two 2.8 mm titanium anchors with ‘#2’ Fiberwire sutures (Arthrex, USA) were inserted into the bone at the border of the footprint of the retinaculum, approximately 2 cm apart. The position and the tension of the retinaculum were examined, and sutures were passed through the retinaculum tissue (figures 3 and 4).

Figure 3.

Posteromedial visualisation of the tibialis posterior tendon (A), tendon retinaculum (B) and prepared retinaculum footprint (C) with two 2.8 mm titanium anchors placed into the bone with ‘#2’ Fiberwire sutures (Arthrex, USA).

Figure 4.

Final result of the anatomic reconstruction of the tibialis posterior tendon retinaculum using two titanium anchors (arrow).

A postoperative plain X-ray displays the titanium anchors on the posterior side of the medial malleolus (figure 5).

Figure 5.

Postoperative X-ray of the left ankle joint in the anteroposterior view (A) and lateral view (B), with two titanium anchors (arrow) in the posterior part of the medial malleolus.

Cast immobilisation was used for 2 weeks, followed by 4 weeks of further immobilisation with an Aircast Walker boot (Berg, Carlsbad, US).

As there are no rehabilitation guidelines available for tibialis posterior tendon retinaculum reconstruction, rehabilitation guidelines for lateral ankle ligament repair were used.^{14 15}

The patient started a home-based rehabilitation programme 2 weeks after surgery. The first phase included isometric exercises for ankle inversion and eversion and non-weight-bearing active- range-of-motion exercises for plantar and dorsiflexion. Functional exercises for knee and hip muscles were also started at that time. Weight bearing in an applied Aircast Walker was permitted with 50% of the bodyweight. Use of the boot was discontinued 6 weeks postoperatively, and transition to walking with full bodyweight without assisting devices was started. Progressive gait training and proprioceptive exercises were performed from week six onwards. At 12 weeks, postoperative complex balance exercises and gradual resistance training for the ankle muscles were started. The patient continued with balance and strength training until 1 year after surgery.

Outcome and follow-up

The EFAS and Foot and Ankle Outcome score (FAOS) were assessed before surgery and at 2, 6, 12 and 19 months postoperatively.

Bilateral isokinetic strength tests (Humac Norm, USA) for ankle inversion and eversion at 30°/sec and 120°/sec were performed at 6, 12 and 19 months postoperatively. Range of motion (ROM) of the ankle joint was measured using the ankle lunge test at the same time intervals. The Y-balance test was used to evaluate functional performance.

The EFAS and FAOS scores are presented in table 1. The isokinetic strength tests are presented in table 2. Plantar flexion, inversion and eversion strength was restored within the first eight postoperative weeks, while dorsiflexion continued to improve until 6 months after surgery.

Discussion

Surgical reconstruction of the unstable tibialis posterior tendon retinaculum followed by a long-term patient-based rehabilitation programme resulted in a slow but full recovery of the ankle joint.

Traumatic dislocation of the tibialis posterior tendon is an uncommon injury. However, Prato et al⁹ speculate that it might be more common than diagnosed. It is often caused by a twisting injury with plantar hyperflexion and inversion in the varus position of the ankle joint during sporting activities or other high-energy accidents.^{3 7} The patient in question here injured her ankle during downhill skiing. Downhill skiing is an extreme type of sport, with a high rate of serious leg injuries.¹⁶ Even though a high-cut type of boot is used during alpine skiing, serious ankle injury can occur. It can be misdiagnosed as a typical ankle sprain or ligament injury because of swelling around the medial malleolus and ankle joint, which means it is not possible to palpate the tendon in acute cases; therefore, it may be mistreated.⁷ In chronic cases, it can also be difficult to diagnose, and the examiner needs to be experienced. Posteromedial pain was the main reason that examination and imaging investigations were focused on this particular region. With the cooperation of the patient, careful examination enabled visualisation of the unstable and painful tibialis posterior tendon.

Plain X-rays are needed to rule out fractures, as in the present case. US is a useful tool to detect pathological changes^{7 9} during motion of the tendon, focusing on its position in the posterior part of the medial malleolus.¹⁰ MRI scans can be used to assess the position of the tibialis posterior tendon and the anatomy of both the posterior retinaculum and the tendon sheath.³ US was not available, and, therefore, an MRI scan was obtained; this revealed a dislocated tibialis posterior tendon with synovitis around the tendon and an injured retinaculum.

There are a limited number of reported cases of the tibialis posterior tendon dislocations in the literature, and only one study by Ouzounian and Myerson,¹³ which involved a bigger case series with seven patients, reported that failed conservative treatment followed by late-phase surgical reconstruction results in a high success rate. Based on the available literature, surgical treatment was already suggested to the patient in the current study at the first consultation. Due to personal reasons of the patient the surgery was postponed. It was performed 2 months after the initial visit and 4 months after the traumatic episode.

Retinaculum repair with tendon reduction is the recommended treatment option in tibialis posterior tendon dislocation cases. There are several types of reconstructions covered in the literature: the Das De procedure,¹¹ transosseous suture fixation,^{3 7} anchor fixation and an Achilles tendon flap.¹⁷ Additional methods have been also described, such as bone block reconstruction,⁵ tendon groove deepening^{6 7} and suture tape reconstruction.¹² In the present case, anatomic reconstruction of the tibialis posterior tendon retinaculum was possible, and there was no need for additional procedures.

Most case reports involve short descriptions of the rehabilitation programmes, which commonly involve range-of-motion exercises and jogging.1–7 10 11 17

In the present case report, PROM results and long-term lower leg muscle recovery are reported.

It appears that for the present case report, the patient’s personalised rehabilitation programme resulted in full muscle recovery after a shorter time than reported in the literature.⁷ However, according to FAOS and EFAS scores, patient reached full recovery after as much as 19 months. One must pay attention to the fact that a flat-type anatomy of the tendon groove might be a risk factor for slow recovery. In such cases, tendon groove deepening as an additional procedure might be considered.

This study has two main weaknesses. First, no comparison with acute and delayed reconstruction could be made, and second, this is only a case report.

Patient’s perspective.

Patient’s comments: when I had a left ankle trauma from downhill skiing at the end of 2019, I thought it was a simple ankle sprain. As I am a professional physiotherapist, I started a well-known ankle sprain rehabilitation programme. However, after the first visit to the orthopaedic surgeon, we understood that the situation was more complex. I was still keen to continue with the conservative treatment, but it soon became clear that I had to undergo surgical intervention. After the operation, the recovery was much slower than I expected. It took 1 year of a well-guided rehabilitation programme to reach my previous physical fitness level. I would definitely suggest early surgical intervention for faster recovery for future patients.

Learning points.

• Traumatic dislocation of the tibialis posterior tendon is an uncommon injury.

• It can be misdiagnosed as a typical ankle sprain or ligament injury because of swelling around the medial malleolus and ankle joint.

• Tendon reduction and retinaculum repair are the recommended treatment options.

• Tendon groove deepening must be considered in the presence of a flat-type anatomy of the original tendon groove.

• The personalised rehabilitation programme of the patient in this case resulted in full muscle recovery after 6 months.

• According to Foot and Ankle Outcome Score, European Foot and Ankle Society Score and Patient-reported outcome measurement Score, patient showed full recovery after 19 months; this study indicates that muscle recovery can be reached earlier.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s)