A Guide To Shoe Gear Selection Following A Transmetatarsal Amputation

Proper shoe gear/bracing and education on the importance of its use is essential in the long-term postoperative management of patients who have undergone a transmetatarsal amputation (TMA). Initial publications on shoe gear use after a TMA reported that patients did well with no more than the placement of lamb’s wool in the toe box of a standard shoe.1-5

   However, in 1963, Bauman and colleagues noted that “a foot without toes is urgently in need of protection.”6 They performed a comparison study of six different combinations of shoe sole modifications and orthotics, and their ability to reduce plantar foot pressures. The authors found that shoes with a rigid sole reduced plantar forefoot pressures significantly during the late stance and push-off phases of gait. The addition of a rocker bottom sole with the apex at the center of the shoe was the most effective in reducing plantar forefoot pressures in the shortened or deformed foot.

   Despite these findings, the use of a standard shoe with a filler in the toe box persisted. This was due to the perception that the functional capacity of a patient who had undergone a TMA was not significantly different than that of a non-amputee due to maintenance of a majority of the foot and the length of the limb.7

   Mueller and co-workers found that patients who had undergone a TMA lacked stability.8-10 The authors hypothesized the primary mechanical reason for this was loss of the available moment arm length required to generate the plantarflexory force necessary for ambulation due to loss of the forefoot.

   Spurred by these findings, Mueller and colleagues then compared the functional differences between transmetatarsal amputation patients and a non-amputee control group who were matched for age, gender, height, weight and body mass index.8-10 Patients with a TMA had a significantly decreased functional capacity in comparison to non-amputees, being particularly poor at performing activities that required body weight to shift to the front of the foot. These activities included reaching, climbing stairs and walking at a normal pace. Patients with a TMA also had walking speeds similar to patients with severe intermittent claudication.

   Kelly and co-workers had similar findings when comparing patients with diabetes and a TMA to an age matched control group of non-amputees without diabetes.11 Peak plantar pressures were 16 percent higher and walking speed was 25 meters per minute slower in the patients with a TMA when ambulating in their normal shoe gear with lamb’s wool in the toe box.

Weighing The Efficacy Of Shoes, Orthoses And Bracing For TMA Patients

Mueller and colleagues performed a study to determine what combination of orthotics, shoe gear and/or bracing would be most efficacious in returning patients with a TMA to a more normal functional capacity postoperatively.10

   The study involved 30 patients with a diagnosis of diabetes who had undergone a TMA. The mean age of the patients was 61.7 ± 4 years. The mean duration of diabetes was 19.9 ± 10.1 years. All patients had a fully healed TMA with a mean time of 27.4 ± 28.1 months since amputation and were able to ambulate without the use of an assistive device.

   The researchers studied the following six combinations of orthotics, shoe gear and bracing:10
• the patient’s own full length shoe with lamb’s wool in the toe box;
• a custom full length shoe with a total contact insert (TCI) and an ankle foot orthosis (AFO);
• a custom full length shoe with a rocker bottom sole (RBS) and a TCI;
• a custom full length shoe with a rocker bottom sole, a total contact insert and an AFO;
• a custom shortened shoe with a rocker bottom sole and a total contact insert; and
• a custom shortened shoe with a rocker bottom sole, a total contact insert and an AFO (see the below table “How Shoe/Orthotic And Bracing Combinations Compare With Lamb’s Wool In The Toe Box”).

   The total contact insert was custom molded and fabricated with ½-inch of white Plastazote and 3/16-inch polypropylene plastic. The rocker bottom sole was just proximal to the residual metatarsals and was fabricated at a 20 degree angle. The patients received instructions to wear each combination of orthotics, shoe gear and/or bracing for 30 days.

   When comparing these combinations to the use of a full-length shoe with lamb’s wool in the toe box, the authors noted improvements in functional capacity and walking speed with the use of a custom full length or shortened shoe with a rocker bottom sole and a total contact insert, and with the use of a custom shortened shoe with a rocker bottom sole, a total contact insert and an AFO.10 The authors defined functional capacity as activities such as putting a book on a shelf, donning and doffing a jacket, picking a penny up from the floor, walking 50 feet with a turn and climbing one flight of stairs.

   In the study, ipsilateral peak plantar pressures were decreased for every combination of rocker bottom sole, total contact insert and AFO in comparison to the patient’s own full length shoe with the lamb’s wool in the toe box.10 Plantar pressures to the contralateral limb were decreased for every combination in comparison to the patient’s own full length shoe with the lamb’s wool in the toe box, except for those with a shortened shoe. More than 50 percent of the patients did not tolerate the combinations with the AFO due to the restricted ankle joint motion. Patients with an associated dropfoot or proximal TMA did find the addition of an AFO beneficial.

   In terms of cosmesis, the combinations involving custom shortened shoes were the least tolerated with most patients refusing to wear them.10 The four patients with a bilateral TMA did like the shortened shoes due to the ability to make the shoes similar in appearance.

   The most widely accepted combination in terms of patient adherence with use was the custom full length shoe with a rocker bottom sole and total contact insert.10 A total of 86 percent of the patients completed the entire 30-day use of this combination.

   Contrast this with only 43 percent of patients who completed the entire 30-day course of use of their own full length shoe gear with lamb’s wool in the toe box.10 The custom shortened shoe with a rocker bottom sole and total contact insert was the second highest combination when it came to rate of adherence with 70 percent of patients completing the entire 30-day course of use.

Further Insights On Shoe Modifications

Research has found the use of a rocker bottom sole decreases peak plantar pressures up to 50 percent in the central forefoot.12 The addition of a steel shank in the sole of the shoe or a carbon fiber plate in the shoe has been another option in prosthetic management of the patient with a TMA.

   Studies have found both of these modifications aid in increasing the shoe’s stability, limiting distortion of the shoe and aiding in generating ankle plantarflexory power due to recreation of the rigid lever arm lost with amputation of the forefoot.13,14 Researchers have shown that use of a total contact insert in a custom molded high type shoe with a rocker bottom sole decreases pressure to both the forefoot and the heel.12

   One must ensure proper placement of the apex of the rocker bottom sole in order to decrease plantar forefoot pressures. If the apex is under or just proximal to the distal metatarsal, the clinician can increase plantar pressures under the fifth metatarsal.14 Proper placement of the apex of the rocker bottom sole proximal to the residual metatarsals and consideration of previously described tendon balancing techniques to reduce varus deformity of the residual foot are imperative to aid in reducing plantar pressures under the entire forefoot.15,16

In Conclusion

The goal of long-term management of the patient who has undergone a TMA is to return or improve upon the patient’s ambulatory status postoperatively and minimize the potential for further breakdown of the residual foot.5,7,13 Orthotics, shoe gear and bracing are essential to this goal. The proper combination of these will augment stability, aid in ambulation and protect the residual forefoot from increased pressure and shear strain.

   In addition, the selection of shoe gear and/or bracing should be cosmetically appealing to the patient to promote and maintain their use. From the studies to date, the use of a custom or customized full length shoe with a rocker bottom sole and total contact insert meets all of these goals. One should consider an AFO in patients with an associated dropfoot deformity or proximal TMA.

   Physicians must work with certified orthotists and pedorthists, and educate patients on the importance of lifelong use of these items to minimize future complications.

   Dr. Schade is the Chief of the Limb Preservation Service and the Director of the Complex Lower Extremity Surgery and Research Fellowship at Madigan Healthcare System in Tacoma, Wash.

References

1. Warren R, Crawford ED, Hardy IB, McKittrick JB. The transmetatarsal amputation in arterial deficiency of the lower extremity. Surgery. 1952; 31(1):132-140.
2. Pedersen HE, Day, AJ. The transmetatarsal amputation in peripheral vascular disease. J Bone Joint Surg Am. 1954; 36-A(6):1190-1198.
3. McKittrick JB, Root HF, Wheelock FC. Evaluation of the transmetatarsal amputation in patients with diabetes mellitus. Surgery. 1957; 41(2):184-189.
4. Rosendahl S. Transmetatarsal amputation in diabetic gangrene. Acta Orthop Scand. 1972; 43(1):78-83.
5. Levy SE. Total contact restoration prosthesis for partial foot amputations. J Am Podiatr Assoc. 1960; 50:887-896.
6. Bauman JH, Girling JP, Brand PW. Plantar pressures and trophic ulceration. An evaluation of footwear. J Bone Joint Surg. 1963; 45:652-673.
7. Garbalosa JC, Cavanagh PR, Wu G, Ulbrecht JS, Becker MB, Alexander IJ, Campbell JH. Foot function in diabetic patients after partial amputation. Foot Ankle Int. 1996; 17(1):43-48.
8. Mueller MJ, Strube MJ. Therapeutic footwear: enhanced function in people with diabetes and transmetatarsal amputation. Arch Phys Med Rehabil. 1997; 78(9):952-956.
9. Mueller MJ, Strube MJ, Allen BT. Therapeutic footwear can reduce plantar pressures in patients with diabetes and transmetatarsal amputation. Diabetes Care. 1997; 20(4):637-641.
10. Mueller M, Strube M, Allen B. Effect of six types of footwear on peak plantar pressures in patients with diabetes and transmetatarsal amputation. Clin Biomech. 1997; 12(3):S3.
11. Kelly VE, Mueller MJ, Sinacore DR. Timing of peak plantar pressure during the stance phase of walking. A study of patients with diabetes mellitus and transmetatarsal amputation. J Am Podiatr Med Assoc. 2000; 90(1):18-23.
12. Praet SF, Louwerens JW. The influence of shoe design on plantar pressures in neuropathic feet. Diabetes Care. 2003; 26(2):441-445.
13. Tang SF, Chen CP, Chen MJ, Chen WP, Leong CP, Chu NK. Transmetatarsal amputation prosthesis with carbon-fiber plate: enhanced gait function. Am J Phys Med Rehabil. 2004; 83(2):124-130.
14. Schaff PS, Cavanagh PR. Shoes for the insensitive foot: the effect of a “rocker bottom” shoe modification on plantar pressure distribution. Foot Ankle. 1990; 11(3):129-140.
15. Nawoczenski DA, Birke JA, Coleman WC. Effect of rocker sole design on plantar forefoot pressures. J Am Podiatr Med Assoc. 1988; 78(9):455-460.
16. Schade VL. Emerging insights on adjunctive procedures with transmetatarsal amputations. Podiatry Today. 2010; 24(3):22-28.

   For further reading, see “Emerging Insights On Adjunctive Procedures With Transmetatarsal Amputations” in the March 2010 issue of Podiatry Today, “A Guide To Transmetatarsal Amputations In Patients With Diabetes” in the July 2006 issue, “Current Considerations In Performing Transmetatarsal Amputations” in the February 2011 issue or “When Is Amputation The Salvage Procedure?” in the March 2010 issue.